Conserved biophysical features of the CaV2 presynaptic Ca2+ channel homologue from the early-diverging animal Trichoplax adhaerens
2020; Elsevier BV; Volume: 295; Issue: 52 Linguagem: Inglês
10.1074/jbc.ra120.015725
ISSN1083-351X
AutoresJulia Gauberg, Salsabil Abdallah, Wassim Elkhatib, Alicia N. Harracksingh, Thomas Piekut, Elise F. Stanley, Adriano Senatore,
Tópico(s)Neuroscience and Neuropharmacology Research
ResumoThe dominant role of CaV2 voltage-gated calcium channels for driving neurotransmitter release is broadly conserved. Given the overlapping functional properties of CaV2 and CaV1 channels, and less so CaV3 channels, it is unclear why there have not been major shifts toward dependence on other CaV channels for synaptic transmission. Here, we provide a structural and functional profile of the CaV2 channel cloned from the early-diverging animal Trichoplax adhaerens, which lacks a nervous system but possesses single gene homologues for CaV1–CaV3 channels. Remarkably, the highly divergent channel possesses similar features as human CaV2.1 and other CaV2 channels, including high voltage–activated currents that are larger in external Ba2+ than in Ca2+; voltage-dependent kinetics of activation, inactivation, and deactivation; and bimodal recovery from inactivation. Altogether, the functional profile of Trichoplax CaV2 suggests that the core features of presynaptic CaV2 channels were established early during animal evolution, after CaV1 and CaV2 channels emerged via proposed gene duplication from an ancestral CaV1/2 type channel. The Trichoplax channel was relatively insensitive to mammalian CaV2 channel blockers ω-agatoxin-IVA and ω-conotoxin-GVIA and to metal cation blockers Cd2+ and Ni2+. Also absent was the capacity for voltage-dependent G-protein inhibition by co-expressed Trichoplax Gβγ subunits, which nevertheless inhibited the human CaV2.1 channel, suggesting that this modulatory capacity evolved via changes in channel sequence/structure, and not G proteins. Last, the Trichoplax channel was immunolocalized in cells that express an endomorphin-like peptide implicated in cell signaling and locomotive behavior and other likely secretory cells, suggesting contributions to regulated exocytosis. The dominant role of CaV2 voltage-gated calcium channels for driving neurotransmitter release is broadly conserved. Given the overlapping functional properties of CaV2 and CaV1 channels, and less so CaV3 channels, it is unclear why there have not been major shifts toward dependence on other CaV channels for synaptic transmission. Here, we provide a structural and functional profile of the CaV2 channel cloned from the early-diverging animal Trichoplax adhaerens, which lacks a nervous system but possesses single gene homologues for CaV1–CaV3 channels. Remarkably, the highly divergent channel possesses similar features as human CaV2.1 and other CaV2 channels, including high voltage–activated currents that are larger in external Ba2+ than in Ca2+; voltage-dependent kinetics of activation, inactivation, and deactivation; and bimodal recovery from inactivation. Altogether, the functional profile of Trichoplax CaV2 suggests that the core features of presynaptic CaV2 channels were established early during animal evolution, after CaV1 and CaV2 channels emerged via proposed gene duplication from an ancestral CaV1/2 type channel. The Trichoplax channel was relatively insensitive to mammalian CaV2 channel blockers ω-agatoxin-IVA and ω-conotoxin-GVIA and to metal cation blockers Cd2+ and Ni2+. Also absent was the capacity for voltage-dependent G-protein inhibition by co-expressed Trichoplax Gβγ subunits, which nevertheless inhibited the human CaV2.1 channel, suggesting that this modulatory capacity evolved via changes in channel sequence/structure, and not G proteins. Last, the Trichoplax channel was immunolocalized in cells that express an endomorphin-like peptide implicated in cell signaling and locomotive behavior and other likely secretory cells, suggesting contributions to regulated exocytosis. Voltage-gated Ca2+ (CaV) channels serve essential functions in excitable cells, imparted by their capacity to translate electrical signals carried by Na+ and K+ channels, into cytoplasmic Ca2+ signals (1Clapham D.E. Calcium signaling.Cell. 2007; 131 (18083096): 1047-105810.1016/j.cell.2007.11.028Abstract Full Text Full Text PDF PubMed Scopus (2496) Google Scholar). For example, CaV channels couple membrane excitation with fusion of presynaptic vesicles, muscle contraction, alterations in nuclear gene expression, and regulation of ciliary beating (2Catterall W.A. Voltage-gated calcium channels.Cold Spring Harb. Perspect. Biol. 2011; 3 (21746798)a00394710.1101/cshperspect.a003947Crossref PubMed Scopus (785) Google Scholar, 3Senatore A. Raiss H. Le P. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: cnidaria, placozoa, porifera and ctenophora.Front. Physiol. 2016; 7 (27867359): 48110.3389/fphys.2016.00481Crossref PubMed Scopus (22) Google Scholar). CaV channels belong to a large family of pore-loop (P-loop) channels that includes voltage-gated Na+ (NaV) channels and K+ (KV) channels (4Pozdnyakov I. Matantseva O. Skarlato S. Diversity and evolution of four-domain voltage-gated cation channels of eukaryotes and their ancestral functional determinants.Sci. Rep. 2018; 8 (29476068)353910.1038/s41598-018-21897-7Crossref PubMed Scopus (14) Google Scholar), named after their four extracellular loop structures that come together in the pore to form the ion selectivity filter, a motif uniquely configured in different channels for selecting Ca2+, Na+, or K+ ions (5MacKinnon R. Pore loops: an emerging theme in ion channel structure.Neuron. 1995; 14 (7538310): 889-89210.1016/0896-6273(95)90327-5Abstract Full Text PDF PubMed Scopus (213) Google Scholar). Humans and related animals possess three types of CaV channels, broadly classified as high and low voltage–activated, the former requiring strong depolarization for activation (i.e. CaV1 or L-type channels and CaV2 or N-, P-/Q-, and R-type channels) and the latter requiring only mild, sub-threshold depolarization (i.e. CaV3 or T-type channels) (6Zamponi G.W. Voltage-gated Calcium Channels. Springer, Berlin2005Google Scholar). Phylogenomic studies have established that most animals possess single gene copies of CaV1–CaV3 channels, whereas gene duplications in vertebrates gave rise to four CaV1 channels (CaV1.1–CaV1.4), three CaV2 channels (CaV2.1–CaV2.3), and three CaV3 channels (CaV3.1–CaV3.3) (3Senatore A. Raiss H. Le P. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: cnidaria, placozoa, porifera and ctenophora.Front. Physiol. 2016; 7 (27867359): 48110.3389/fphys.2016.00481Crossref PubMed Scopus (22) Google Scholar, 4Pozdnyakov I. Matantseva O. Skarlato S. Diversity and evolution of four-domain voltage-gated cation channels of eukaryotes and their ancestral functional determinants.Sci. Rep. 2018; 8 (29476068)353910.1038/s41598-018-21897-7Crossref PubMed Scopus (14) Google Scholar, 7Catterall W.A. Perez-Reyes E. Snutch T.P. Striessnig J. International Union of Pharmacology. XLVIII. Nomenclature and structure-function relationships of voltage-gated calcium channels.Pharmacol. Rev. 2005; 57 (16382099): 411-42510.1124/pr.57.4.5Crossref PubMed Scopus (908) Google Scholar, 8Moran Y. Zakon H.H. The evolution of the four subunits of voltage-gated calcium channels: ancient roots, increasing complexity, and multiple losses.Genome Biol. Evol. 2014; 6 (25146647): 2210-221710.1093/gbe/evu177Crossref PubMed Scopus (22) Google Scholar, 9Jeziorski M.C. Greenberg R.M. Anderson P. The molecular biology of invertebrate voltage-gated Ca2+ channels.J. Exp. Biol. 2000; 203 (10667967): 841-856Crossref PubMed Google Scholar, 10Piekut T. Wong Y.Y. Walker S.E. Smith C.L. Gauberg J. Harracksingh A.N. Lowden C. Novogradac B.B. Cheng H.-Y.M. Spencer G.E. Senatore A. Early metazoan origin and multiple losses of a novel clade of RIM pre-synaptic calcium channel scaffolding protein homologues.Genome Biol. Evol. 2020; 12 (32413100): 1217-123910.1093/gbe/evaa097Crossref PubMed Scopus (1) Google Scholar, 11Spafford J.D. Dunn T. Smit A.B. Syed N.I. Zamponi G.W. In vitro characterization of L-type calcium channels and their contribution to firing behavior in invertebrate respiratory neurons.J. Neurophysiol. 2006; 95 (16162826): 42-5210.1152/jn.00658.2005Crossref PubMed Scopus (0) Google Scholar). Teleosts have had a further duplication of CaV channel genes, with species like Danio rerio having seven CaV1, six CaV2, and five CaV3 genes (12Haverinen J. Hassinen M. Dash S.N. Vornanen M. Expression of calcium channel transcripts in the zebrafish heart: dominance of T-type channels.J. Exp. Biol. 2018; 221 (jeb.179226) (29739832)10.1242/jeb.179226Crossref PubMed Scopus (4) Google Scholar). Independently, the cnidarians (e.g. jellyfish) duplicated CaV2 and CaV3 channel genes, resulting in a repertoire of a single CaV1 channel, three CaV2 channels, and two CaV3 channels. The earliest diverging animal lineages possess only CaV2 channels (ctenophores), CaV1 channels (sponges), or an evolutionary precursor of CaV1 and CaV2 channels, dubbed CaV1/2 channels (sponges) (3Senatore A. Raiss H. Le P. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: cnidaria, placozoa, porifera and ctenophora.Front. Physiol. 2016; 7 (27867359): 48110.3389/fphys.2016.00481Crossref PubMed Scopus (22) Google Scholar, 8Moran Y. Zakon H.H. The evolution of the four subunits of voltage-gated calcium channels: ancient roots, increasing complexity, and multiple losses.Genome Biol. Evol. 2014; 6 (25146647): 2210-221710.1093/gbe/evu177Crossref PubMed Scopus (22) Google Scholar, 10Piekut T. Wong Y.Y. Walker S.E. Smith C.L. Gauberg J. Harracksingh A.N. Lowden C. Novogradac B.B. Cheng H.-Y.M. Spencer G.E. Senatore A. Early metazoan origin and multiple losses of a novel clade of RIM pre-synaptic calcium channel scaffolding protein homologues.Genome Biol. Evol. 2020; 12 (32413100): 1217-123910.1093/gbe/evaa097Crossref PubMed Scopus (1) Google Scholar). The most early-diverging animals to possess all three CaV channel types (i.e. CaV1–CaV3) are the placozoans (3Senatore A. Raiss H. Le P. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: cnidaria, placozoa, porifera and ctenophora.Front. Physiol. 2016; 7 (27867359): 48110.3389/fphys.2016.00481Crossref PubMed Scopus (22) Google Scholar, 8Moran Y. Zakon H.H. The evolution of the four subunits of voltage-gated calcium channels: ancient roots, increasing complexity, and multiple losses.Genome Biol. Evol. 2014; 6 (25146647): 2210-221710.1093/gbe/evu177Crossref PubMed Scopus (22) Google Scholar, 10Piekut T. Wong Y.Y. Walker S.E. Smith C.L. Gauberg J. Harracksingh A.N. Lowden C. Novogradac B.B. Cheng H.-Y.M. Spencer G.E. Senatore A. Early metazoan origin and multiple losses of a novel clade of RIM pre-synaptic calcium channel scaffolding protein homologues.Genome Biol. Evol. 2020; 12 (32413100): 1217-123910.1093/gbe/evaa097Crossref PubMed Scopus (1) Google Scholar), a phylum of simple seawater animals that includes the species Trichoplax adhaerens and Hoilungia hongkongensis (13Eitel M. Francis W.R. Varoqueaux F. Daraspe J. Osigus H.-J. Krebs S. Vargas S. Blum H. Williams G.A. Schierwater B. Wörheide G. Comparative genomics and the nature of placozoan species.PLoS Biol. 2018; 16 (30063702)e200535910.1371/journal.pbio.2005359Crossref PubMed Scopus (31) Google Scholar, 14Srivastava M. Begovic E. Chapman J. Putnam N.H. Hellsten U. Kawashima T. Kuo A. Mitros T. Salamov A. Carpenter M.L. Signorovitch A.Y. Moreno M.A. Kamm K. Grimwood J. Schmutz J. et al.The Trichoplax genome and the nature of placozoans.Nature. 2008; 454 (18719581): 955-96010.1038/nature07191Crossref PubMed Scopus (590) Google Scholar). A unique feature of placozoans is that they lack neurons, synapses, and muscle (15Smith C.L. Varoqueaux F. Kittelmann M. Azzam R.N. Cooper B. Winters C.A. Eitel M. Fasshauer D. Reese T.S. Novel cell types, neurosecretory cells, and body plan of the early-diverging metazoan Trichoplax adhaerens.Curr. Biol. 2014; 24 (24954051): 1565-157210.1016/j.cub.2014.05.046Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar, 16Schierwater B. My favorite animal, Trichoplax adhaerens.BioEssays. 2005; 27 (16299758): 1294-130210.1002/bies.20320Crossref PubMed Scopus (97) Google Scholar) and yet bear distinct cell types whose activity is coordinated for the purpose of motile behaviors such as feeding (17Smith C.L. Pivovarova N. Reese T.S. Coordinated feeding behavior in Trichoplax, an animal without synapses.PLoS One. 2015; 10 (26333190)e013609810.1371/journal.pone.0136098Crossref PubMed Scopus (48) Google Scholar, 18Senatore A. Reese T.S. Smith C.L. Neuropeptidergic integration of behavior in Trichoplax adhaerens, an animal without synapses.J. Exp. Biol. 2017; 220 (28931721): 3381-339010.1242/jeb.162396Crossref PubMed Scopus (43) Google Scholar), chemotaxis (19Smith C.L. Reese T.S. Govezensky T. Barrio R.A. Coherent directed movement toward food modeled in Trichoplax, a ciliated animal lacking a nervous system.Proc. Natl. Acad. Sci. U. S. A. 2019; 116 (30979806): 8901-890810.1073/pnas.1815655116Crossref PubMed Scopus (18) Google Scholar, 20Heyland A. Croll R. Goodall S. Kranyak J. Wyeth R. Trichoplax adhaerens, an enigmatic basal metazoan with potential.in: Carroll D.J. Stricker S.A. Developmental Biology of the Sea Urchin and Other Marine Invertebrates. Springer, Berlin2014: 45-61Crossref Scopus (12) Google Scholar, 21Romanova D.Y. Heyland A. Sohn D. Kohn A.B. Fasshauer D. Varoqueaux F. Moroz L.L. Glycine as a signaling molecule and chemoattractant in Trichoplax (Placozoa): insights into the early evolution of neurotransmitters.NeuroReport. 2020; 31 (32243353): 490-49710.1097/WNR.0000000000001436Crossref PubMed Scopus (4) Google Scholar), phototaxis (20Heyland A. Croll R. Goodall S. Kranyak J. Wyeth R. Trichoplax adhaerens, an enigmatic basal metazoan with potential.in: Carroll D.J. Stricker S.A. Developmental Biology of the Sea Urchin and Other Marine Invertebrates. Springer, Berlin2014: 45-61Crossref Scopus (12) Google Scholar), and gravitaxis (22Mayorova T.D. Smith C.L. Hammar K. Winters C.A. Pivovarova N.B. Aronova M.A. Leapman R.D. Reese T.S. Cells containing aragonite crystals mediate responses to gravity in Trichoplax adhaerens (Placozoa), an animal lacking neurons and synapses.PLoS One. 2018; 13 (29342202)e019090510.1371/journal.pone.0190905Crossref PubMed Scopus (15) Google Scholar). Notably, despite lacking synapses, increasing evidence suggests that cellular communication in placozoans likely occurs in a protosynaptic manner, where regulated secretion of signaling molecules, such as neuropeptides and small-molecule transmitters, targets membrane receptors on other cells to exert an effect (18Senatore A. Reese T.S. Smith C.L. Neuropeptidergic integration of behavior in Trichoplax adhaerens, an animal without synapses.J. Exp. Biol. 2017; 220 (28931721): 3381-339010.1242/jeb.162396Crossref PubMed Scopus (43) Google Scholar, 21Romanova D.Y. Heyland A. Sohn D. Kohn A.B. Fasshauer D. Varoqueaux F. Moroz L.L. Glycine as a signaling molecule and chemoattractant in Trichoplax (Placozoa): insights into the early evolution of neurotransmitters.NeuroReport. 2020; 31 (32243353): 490-49710.1097/WNR.0000000000001436Crossref PubMed Scopus (4) Google Scholar, 23Mayorova T.D. Hammar K. Winters C.A. Reese T.S. Smith C.L. The ventral epithelium of Trichoplax adhaerens deploys in distinct patterns cells that secrete digestive enzymes, mucus or diverse neuropeptides.Biol. Open. 2019; 8 (31366453)bio04567410.1242/bio.045674Crossref PubMed Scopus (8) Google Scholar, 24Varoqueaux F. Williams E.A. Grandemange S. Truscello L. Kamm K. Schierwater B. Jékely G. Fasshauer D. High cell diversity and complex peptidergic signaling underlie placozoan behavior.Curr. Biol. 2018; 28 (30344118): 3495-3501.e210.1016/j.cub.2018.08.067Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar). In addition to their distinct voltages of activation, CaV channels are distinguished by their differential association with accessory CaVβ and CaVα2δ subunits, which are essential for the proper membrane expression and function of CaV1 and CaV2, but not CaV3 channels (2Catterall W.A. Voltage-gated calcium channels.Cold Spring Harb. Perspect. Biol. 2011; 3 (21746798)a00394710.1101/cshperspect.a003947Crossref PubMed Scopus (785) Google Scholar, 6Zamponi G.W. Voltage-gated Calcium Channels. Springer, Berlin2005Google Scholar). Furthermore, although their cellular functions overlap in certain contexts, there are several functions for which the different channels have specialized, observed nearly ubiquitously in animals ranging from humans to fruit flies to nematode worms (2Catterall W.A. Voltage-gated calcium channels.Cold Spring Harb. Perspect. Biol. 2011; 3 (21746798)a00394710.1101/cshperspect.a003947Crossref PubMed Scopus (785) Google Scholar, 3Senatore A. Raiss H. Le P. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: cnidaria, placozoa, porifera and ctenophora.Front. Physiol. 2016; 7 (27867359): 48110.3389/fphys.2016.00481Crossref PubMed Scopus (22) Google Scholar, 25Tyson J.R. Snutch T.P. Molecular nature of voltage-gated calcium channels: structure and species comparison.Wiley Interdiscip. Rev. Membr. Transp. Signal. 2013; 2: 181-20610.1002/wmts.91Crossref Scopus (16) Google Scholar). For example, endowed by their broadly conserved low activation voltages, CaV3 channels tend to regulate membrane excitability in neurons and muscle, often in the context of rhythmic excitation, or to boost sub-threshold excitation as occurs in neuron dendrites (26Perez-Reyes E. Molecular physiology of low-voltage-activated t-type calcium channels.Physiol. Rev. 2003; 83 (12506128): 117-16110.1152/physrev.00018.2002Crossref PubMed Google Scholar, 27Senatore A. Spafford J.D. Transient and big are key features of an invertebrate T-type channel (LCav3) from the central nervous system of Lymnaea stagnalis.J. Biol. Chem. 2010; 285 (20056611): 7447-745810.1074/jbc.M109.090753Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar, 28Smith C.L. Abdallah S. Wong Y.Y. Le P. Harracksingh A.N. Artinian L. Tamvacakis A.N. Rehder V. Reese T.S. Senatore A. Evolutionary insights into T-type Ca2+ channel structure, function, and ion selectivity from the Trichoplax adhaerens homologue.J. Gen. Physiol. 2017; 149 (28330839): 483-51010.1085/jgp.201611683Crossref PubMed Scopus (19) Google Scholar, 29Jeong K. Lee S. Seo H. Oh Y. Jang D. Choe J. Kim D. Lee J.-H. Jones W.D. Ca-α1T, a fly T-type Ca2+ channel, negatively modulates sleep.Sci. Rep. 2015; 5 (26647714)1789310.1038/srep17893Crossref PubMed Scopus (12) Google Scholar, 30Steger K.A. Shtonda B.B. Thacker C. Snutch T.P. Avery L. The C. elegans T-type calcium channel CCA-1 boosts neuromuscular transmission.J. Exp. Biol. 2005; 208 (15914662): 2191-220310.1242/jeb.01616Crossref PubMed Scopus (43) Google Scholar, 31McKay B.E. McRory J.E. Molineux M.L. Hamid J. Snutch T.P. Zamponi G.W. Turner R.W. CaV3 T-type calcium channel isoforms differentially distribute to somatic and dendritic compartments in rat central neurons.Eur. J. Neurosci. 2006; 24 (17100846): 2581-259410.1111/j.1460-9568.2006.05136.xCrossref PubMed Scopus (0) Google Scholar, 32Ivanov A.I. Calabrese R.L. Intracellular Ca2+ dynamics during spontaneous and evoked activity of leech heart interneurons: low-threshold Ca currents and graded synaptic transmission.J. Neurosci. 2000; 20 (10864951): 4930-494310.1523/JNEUROSCI.20-13-04930.2000Crossref PubMed Google Scholar, 33Senatore A. Guan W. Boone A.N. Spafford J.D. T-type channels become highly permeable to sodium ions using an alternative extracellular turret region (S5-P) outside the selectivity filter.J. Biol. Chem. 2014; 289 (24596098): 11952-1196910.1074/jbc.M114.551473Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar, 34Shtonda B. Avery L. CCA-1, EGL-19 and EXP-2 currents shape action potentials in the Caenorhabditis elegans pharynx.J. Exp. Biol. 2005; 208 (15914661): 2177-219010.1242/jeb.01615Crossref PubMed Scopus (58) Google Scholar). Instead, stronger depolarizing events, such as the action potential, activate CaV2 channels, which are the major drivers of fast, synchronous membrane fusion of synaptic vesicles at the nerve terminal (35Stanley E.F. The nanophysiology of fast transmitter release.Trends Neurosci. 2016; 39 (26896416): 183-19710.1016/j.tins.2016.01.005Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 36Südhof T.C. The presynaptic active zone.Neuron. 2012; 75 (22794257): 11-2510.1016/j.neuron.2012.06.012Abstract Full Text Full Text PDF PubMed Scopus (527) Google Scholar, 37Spafford J.D. Chen L. Feng Z.-P. Smit A.B. Zamponi G.W. Expression and modulation of an invertebrate presynaptic calcium channel α1 subunit homolog.J. Biol. Chem. 2003; 278 (12672808): 21178-2118710.1074/jbc.M302212200Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar, 38Spafford J.D. Munno D.W. van Nierop P. Feng Z.-P. Jarvis S.E. Gallin W.J. Smit A.B. Zamponi G.W. Syed N.I. Calcium channel structural determinants of synaptic transmission between identified invertebrate neurons.J. Biol. Chem. 2003; 278 (12458203): 4258-426710.1074/jbc.M211076200Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar, 39Edmonds B. Klein M. Dale N. Kandel E.R. Contributions of two types of calcium channels to synaptic transmission and plasticity.Science. 1990; 250 (2174573): 1142-114710.1126/science.2174573Crossref PubMed Google Scholar, 40Saheki Y. Bargmann C.I. Presynaptic CaV2 calcium channel traffic requires CALF-1 and the α2δ subunit UNC-36.Nat. Neurosci. 2009; 12 (19718034): 1257-126510.1038/nn.2383Crossref PubMed Scopus (0) Google Scholar, 41Kawasaki F. Zou B. Xu X. Ordway R.W. Active zone localization of presynaptic calcium channels encoded by the cacophony locus of Drosophila.J. Neurosci. 2004; 24 (14715960): 282-28510.1523/JNEUROSCI.3553-03.2004Crossref PubMed Scopus (124) Google Scholar). Similarly, high voltage activation of post-synaptic CaV1 channels in muscles and neurons drives contraction and changes in nuclear gene expression, respectively (2Catterall W.A. Voltage-gated calcium channels.Cold Spring Harb. Perspect. Biol. 2011; 3 (21746798)a00394710.1101/cshperspect.a003947Crossref PubMed Scopus (785) Google Scholar, 11Spafford J.D. Dunn T. Smit A.B. Syed N.I. Zamponi G.W. In vitro characterization of L-type calcium channels and their contribution to firing behavior in invertebrate respiratory neurons.J. Neurophysiol. 2006; 95 (16162826): 42-5210.1152/jn.00658.2005Crossref PubMed Scopus (0) Google Scholar, 33Senatore A. Guan W. Boone A.N. Spafford J.D. T-type channels become highly permeable to sodium ions using an alternative extracellular turret region (S5-P) outside the selectivity filter.J. Biol. Chem. 2014; 289 (24596098): 11952-1196910.1074/jbc.M114.551473Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar, 42Hara Y. Koganezawa M. Yamamoto D. The Dmca1D channel mediates Ca2+ inward currents in Drosophila embryonic muscles.J. Neurogenet. 2015; 29 (26004544): 117-12310.3109/01677063.2015.1054991Crossref PubMed Scopus (0) Google Scholar, 43Collet C. Excitation-contraction coupling in skeletal muscle fibers from adult domestic honeybee.Pflugers Arch. 2009; 458 (19198873): 601-61210.1007/s00424-009-0642-6Crossref PubMed Scopus (21) Google Scholar, 44Eberl D.F. Ren D. Feng G. Lorenz L.J. Van Vactor D. Hall L.M. Genetic and developmental characterization of Dmca1D, a calcium channel α1 subunit gene in Drosophila melanogaster.Genetics. 1998; 148 (9539432): 1159-1169Crossref PubMed Google Scholar, 45Erxleben C. Rathmayer W. A dihydropyridine-sensitive voltage-dependent calcium channel in the sarcolemmal membrane of crustacean muscle.J. Gen. Physiol. 1997; 109 (9089439): 313-32610.1085/jgp.109.3.313Crossref PubMed Scopus (0) Google Scholar, 46Jospin M. Jacquemond V. Mariol M.-C. Ségalat L. Allard B. The L-type voltage-dependent Ca2+ channel EGL-19 controls body wall muscle function in Caenorhabditis elegans.J. Cell Biol. 2002; 159 (12391025): 337-34810.1083/jcb.200203055Crossref PubMed Scopus (71) Google Scholar, 47Di Biase V. Franzini-Armstrong C. Evolution of skeletal type e–c coupling: a novel means of controlling calcium delivery.J. Cell Biol. 2005; 171 (16286507): 695-70410.1083/jcb.200503077Crossref PubMed Scopus (0) Google Scholar, 48Chan J.D. Zhang D. Liu X. Zarowiecki M. Berriman M. Marchant J.S. Utilizing the planarian voltage-gated ion channel transcriptome to resolve a role for a Ca2+ channel in neuromuscular function and regeneration.Biochim. Biophys. Acta Mol. Cell Res. 2017; 1864 (27771293): 1036-104510.1016/j.bbamcr.2016.10.010Crossref PubMed Scopus (10) Google Scholar). Indeed, given the considerable overlap in biophysical, ion-conducting properties of CaV1 and CaV2 channels, it is unclear why they have generally persisted in their unique respective post- and presynaptic functions. Previously, we documented that the CaV2 channel from the placozoan T. adhaerens lacks an acidic C-terminal amino acid motif proposed to be critical for interactions with presynaptic scaffolding proteins, such as Mint and RIM, and broadly conserved in animals with synapses, such as chordates, arthropods, nematodes, and cnidarians (10Piekut T. Wong Y.Y. Walker S.E. Smith C.L. Gauberg J. Harracksingh A.N. Lowden C. Novogradac B.B. Cheng H.-Y.M. Spencer G.E. Senatore A. Early metazoan origin and multiple losses of a novel clade of RIM pre-synaptic calcium channel scaffolding protein homologues.Genome Biol. Evol. 2020; 12 (32413100): 1217-123910.1093/gbe/evaa097Crossref PubMed Scopus (1) Google Scholar). CaV1 channels also bear deeply conserved C-terminal motifs for interactions with post-synaptic proteins like Shank and Erbin (10Piekut T. Wong Y.Y. Walker S.E. Smith C.L. Gauberg J. Harracksingh A.N. Lowden C. Novogradac B.B. Cheng H.-Y.M. Spencer G.E. Senatore A. Early metazoan origin and multiple losses of a novel clade of RIM pre-synaptic calcium channel scaffolding protein homologues.Genome Biol. Evol. 2020; 12 (32413100): 1217-123910.1093/gbe/evaa097Crossref PubMed Scopus (1) Google Scholar). This suggests that a key evolutionary adaptation toward the specialization of CaV1 and CaV2 channels for distinct post- and presynaptic functions might have involved differential incorporation into protein complexes that would control trafficking and subcellular localization. Following the proposed CaV1/CaV2 split (8Moran Y. Zakon H.H. The evolution of the four subunits of voltage-gated calcium channels: ancient roots, increasing complexity, and multiple losses.Genome Biol. Evol. 2014; 6 (25146647): 2210-221710.1093/gbe/evu177Crossref PubMed Scopus (22) Google Scholar, 10Piekut T. Wong Y.Y. Walker S.E. Smith C.L. Gauberg J. Harracksingh A.N. Lowden C. Novogradac B.B. Cheng H.-Y.M. Spencer G.E. Senatore A. Early metazoan origin and multiple losses of a novel clade of RIM pre-synaptic calcium channel scaffolding protein homologues.Genome Biol. Evol. 2020; 12 (32413100): 1217-123910.1093/gbe/evaa097Crossref PubMed Scopus (1) Google Scholar), the two channel types might have also evolved biophysical features that distinguished them from each other. In the context of fast presynaptic exocytosis, ancestral CaV2 channels might thus have borne unique biophysical features that made them particularly well-suited for this role. Given that placozoans lack synapses but are the most early-diverging animals to possess both CaV1 and CaV2 channels, they present an opportunity to address this question. Here, we sought to explore whether the CaV2 channel from T. adhaerens exhibits biophysical features consistent with those of the major presynaptic CaV2 channel isotype from humans, CaV2.1. Cloning and in vitro expression of the Trichoplax CaV2 channel, coupled with whole-cell patch-clamp electrophysiology, allowed us to compare its ion-conducting properties with those of human CaV2.1 (49Hirano M. Takada Y. Wong C.F. Yamaguchi K. Kotani H. Kurokawa T. Mori M.X. Snutch T.P. Ronjat M. De Waard M. Mori Y. C-terminal splice variants of P/Q-type Ca2+ channel CaV2.1 α1 subunits are differentially regulated by Rab3-interacting molecule proteins.J. Biol. Chem. 2017; 292 (28377503): 9365-938110.1074/jbc.M117.778829Abstract Full Text Full Text PDF PubMed Scopus (17) Google Scholar). Remarkably, despite roughly 600 million years of divergence, the Trichoplax channel exhibited functional features similar to those of the human channel, and its biophysical properties differed from those of the previously cloned Trichoplax low voltage–activated CaV3 channel (28Smith C.L. Abdallah S. Wong Y.Y. Le P. Harracksingh A.N. Artinian L. Tamvacakis A.N. Rehder V. Reese T.S. Senatore A. Evolutionary insights into T-type Ca2+ channel structure, function, and ion selectivity from the Trichoplax adhaerens homologue.J. Gen. Physiol. 2017; 149 (28330839): 483-51010.1085/jgp.201611683Crossref PubMed Scopus (19) Google Scholar). Altogether, the work provides some important insights into the core features of synaptic CaV2 channels, contributing to our understanding of the evolution of CaV channel function in animals. Previously, we identified a single putative Trichoplax CaV2 (TCaV2) channel transcript, bearing a complete protein-coding sequence, in a whole-animal mRNA transcriptome (10Piekut T. Wong Y.Y. Walker S.E. Smith C.L. Gauberg J. Harracksingh A.N. Lowden C. Novogradac B.B. Cheng H.-Y.M. Spencer G.E. Senatore A. Early metazoan origin and multiple losses of a novel clade of RIM pre-synaptic calcium channel scaffolding protein homologues.Genome Biol. Evol. 2020; 12 (32413100): 1217-123910.1093/gbe/evaa097Crossref PubMed Scopus (1) Google Scholar, 50Wong Y.Y. Le P. Elkhatib W. Piekut T. Senatore A. Transcriptome profiling of Trichoplax adhaerens highlights its digestive epithelium and a rich set of genes for fast electrogenic and slow neuromodulatory cellular signaling.Research Square. 2019; 10.21203/rs.2.14504/v1Google Scholar). The TCaV
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