Choose your partners for the next dance: implied PGRMC1 roles in membrane trafficking and mitochondrial modulation
2020; Elsevier BV; Volume: 113; Issue: 5 Linguagem: Inglês
10.1016/j.fertnstert.2020.01.029
ISSN1556-5653
Autores Tópico(s)Neuroendocrine regulation and behavior
ResumoThis commentary considers the study by Salsano et al. (1Salsano S. González-Martín R. Quiñonero A. López-Martín S. Gómez-Escribano A.P. Pérez-Debén S. et al.Novel non-classic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualization.Fertil Steril. 2020; 113: 1050-1066Abstract Full Text Full Text PDF Scopus (17) Google Scholar) while integrating implications from other very recent work. Progesterone (P4) receptor membrane component (PGRMC) 1 is a multifunctional cytochrome b5 (Cytb5) domain protein. It is completely unrelated to the classic/nuclear P4 receptor (P4R). Its steroid-related biology is perhaps a billion years older. Nuclear steroid receptors, including P4R, did not appear until early in chordate evolution, whereas PGRMC1-family proteins regulate sterol synthesis from yeast to mammals (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar) (see literature cited in the bibliographies of the cited references for some concepts discussed in this article due to citation limitations) and can confer progestogen responsiveness to, e.g., bilaterian animals that synthesize no P4. PGRMC1 is the archetypal membrane-associated progesterone receptor (MAPR) family member (1Salsano S. González-Martín R. Quiñonero A. López-Martín S. Gómez-Escribano A.P. Pérez-Debén S. et al.Novel non-classic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualization.Fertil Steril. 2020; 113: 1050-1066Abstract Full Text Full Text PDF Scopus (17) Google Scholar, 2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar). It was originally identified from various organisms in seemingly disparate biological contexts, including dioxin stress response, kidney steroidogenesis, early embryologic axon guidance, and as a component of a membrane-localized P4 receptor (whence the name PGRMC) (1Salsano S. González-Martín R. Quiñonero A. López-Martín S. Gómez-Escribano A.P. Pérez-Debén S. et al.Novel non-classic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualization.Fertil Steril. 2020; 113: 1050-1066Abstract Full Text Full Text PDF Scopus (17) Google Scholar). Very probably, several different processes are activated by separate PGRMC1 functions in these systems. Decidualization is a process developed by mammals whereby uterine endometrial stromal cells undergo functional differentiation from elongated fibroblast-like mesenchymal cells into rounded cells in preparation for embryo implantation. It occurs in marsupial and placental but not monotreme mammals. Salsano et al. explore the role of PGRMC1 in decidualization, describing the identification of proteins present in immunoprecipitation complexes with PGRMC1 before and after the process of decidualization of endometrial fibroblast-like stromal cells (1Salsano S. González-Martín R. Quiñonero A. López-Martín S. Gómez-Escribano A.P. Pérez-Debén S. et al.Novel non-classic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualization.Fertil Steril. 2020; 113: 1050-1066Abstract Full Text Full Text PDF Scopus (17) Google Scholar). Laudably, they used cultured primary human endometrial stromal cells (ESCs) from a clinical setting, directly relevant to human fertility. Although the P4-dependent pseudodecidualization process was necessarily induced in vitro rather than in vivo, two separate protocols both yielded broadly similar results that probably resemble in vivo biology. Most of the PGRMC1-coprecipitated proteins were involved with endomembrane trafficking/cytoskeleton or mitochondrial function (about half in each category). Accordingly, membrane trafficking and mitochondrial functions are likely to be important for PGRMC1. The recent observation that PGRMC2 heme chaperoning to the nucleus affects mitochondrial function is extremely relevant to mitochondrial proteins (3Galmozzi A. Kok B.P. Kim A.S. Montenegro-Burke J.R. Lee J.Y. Spreafico R. et al.PGRMC2 is an intracellular haem chaperone critical for adipocyte function.Nature. 2019; 576: 138-142Crossref PubMed Scopus (57) Google Scholar). Because phosphorylation plays an important part in PGRMC1 biology (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar, 4Thejer B.M. Adhikary P.P. Kaur A. Teakel S.L. van Oosterum A. Seth I. et al.PGRMC1 phosphorylation affects cell shape, motility, glycolysis, mitochondrial form and function, and tumor growth.BMC Mol Cell Biol. 2020; 21: 24Crossref Scopus (27) Google Scholar), and because Salsano et al. used bacterially expressed and nonphosphorylated glutathione-S-transferase (GST) labeled PGRMC1 as bait in the coimmunoprecipitation studies, it is difficult to interpret whether all particular identified coprecipitated proteins from cell lysates actually interact with PGRMC1 in cells under the given experimental condition examined, or whether perhaps some interactions with endogenous PGRMC1 were attenuated by treatment, making more protein available to interact with the GST bait protein, or vice versa (Fig. 1). We would also not expect all PGRMC1 phosphorylation-dependent protein interactions to be detected. Nevertheless the study provides initial insights into the types of proteins proximal to PGRMC1 in these cells. Further characterization will be required to fully understand the biology. Note that while some of the identified proteins potentially make physical contact with PGRMC1, it is possible that many or most are indirectly precipitated as parts of multimolecular macrocomplexes. To investigate whether PGRMC1 unique functions may be separately addressable, my colleagues and I have examined the evolutionary acquisition of conserved sequences as a basis to identify important functionally conserved elements (Fig. 2). MAPR proteins are widespread in eukaryotes, and the PGRMC1-like subfamily was present in at least the common ancestor of yeasts and humans where it was involved in steroidogenic heme binding and cytochrome P450 interactions (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar). The C-terminal extension to the PGRMC1 Cytb5 domain, with its tyrosine phosphorylated Y180 and C-terminal tandem positive charge (RK 192-3) motif (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar), was absent from the earliest animals but had appeared by the time of the last eumetazoan common ancestor, as had Y139 (Fig. 2). (Residue numbering refers to human PGRMC1.) Y139 and Y180 are phosphate acceptors of predicted Src homology 2 (SH2) domain target motifs, which are thought to mediate inducible protein interactions with SH2 domain–containing proteins (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar). The evolution of bilaterally symmetrical animals saw the appearance of conserved phosphoacceptors at T178 and S181 (Fig. 2B). This acquisitory time frame (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar) coincides with the appearance of both the eumetazoan gastrulation organizer and bilaterian germline/somatic segregation. The former underlies eumetazoan body pattern formation and cell differentiation mechanisms, and the latter is central to reproductive biology. My group has recently shown that mutation of the Y180/S181 SH2 target motif, along with S57 next to the SH3 protein interaction target motif (which is adjacent to the Y180 SH2 target motif in the folded protein), leads to a similar rounding of elongated cultured cancer cells to that which occurs during decidualization. This was associated with elevated abundance of some actin-cytoskeletal proteins, increased motility, and dramatic effects on mitochondrial function (4Thejer B.M. Adhikary P.P. Kaur A. Teakel S.L. van Oosterum A. Seth I. et al.PGRMC1 phosphorylation affects cell shape, motility, glycolysis, mitochondrial form and function, and tumor growth.BMC Mol Cell Biol. 2020; 21: 24Crossref Scopus (27) Google Scholar), perhaps reflecting processes underlying those implicated in decidualization. The effect was dependent on Rho-associated protein kinase 1 and accompanied by Y180-dependent PI3K/Akt pathway activity (4Thejer B.M. Adhikary P.P. Kaur A. Teakel S.L. van Oosterum A. Seth I. et al.PGRMC1 phosphorylation affects cell shape, motility, glycolysis, mitochondrial form and function, and tumor growth.BMC Mol Cell Biol. 2020; 21: 24Crossref Scopus (27) Google Scholar). In another study we found that the MAPR interhelical insertion region (MIHIR) in the PGRMC1 Cytb5 domain contains a predicted coiled-coil motif (Fig. 2B) similar to a region found in the coiled-coil region of many myosins, which we speculated could be involved in membrane trafficking via the actin cytoskeleton (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar). We also performed a similar experiment to that of Salsano et al., identifying PGRMC1-coimmunoprecipitated proteins in our cancer cells. About 30% of the significantly associated proteins in our system were associated with actin cytoskeleton, and many of these were displaced by the presumed PGRMC1 inhibitor AG-205 (5Teakel S.L. Ludescher M. Thejer B.M. Poschmann G. Forwood J.K. Neubauer H. et al.Poschmann G, Forwood JK, Neubauer H, et al. Protein complexes including PGRMC1 and actin-associated proteins are disrupted by AG-205.Biochem Biophys Res Commun. 2020; 524: 64-69Crossref Scopus (21) Google Scholar). [Note that although PGRMC1 function is affected by AG-205, it has never been demonstrated that AG-205 is specific for PGRMC1 (5Teakel S.L. Ludescher M. Thejer B.M. Poschmann G. Forwood J.K. Neubauer H. et al.Poschmann G, Forwood JK, Neubauer H, et al. Protein complexes including PGRMC1 and actin-associated proteins are disrupted by AG-205.Biochem Biophys Res Commun. 2020; 524: 64-69Crossref Scopus (21) Google Scholar).] Some mitochondrial proteins were also detected, but not those from Salsano et al. Sources of differences in identified PGRMC1-associated proteins between the studies could include cell-type expression differences (cultured cancer versus endometrial stromal cells), or our use of intracellularly expressed tagged protein bait, which could be post-translationally modified. Notably in this respect, Sabbir recently identified proteins that putatively interact with PGRMC1 post-translational modifications which do not include actin cytoskeletal or mitochondrial proteins (4Thejer B.M. Adhikary P.P. Kaur A. Teakel S.L. van Oosterum A. Seth I. et al.PGRMC1 phosphorylation affects cell shape, motility, glycolysis, mitochondrial form and function, and tumor growth.BMC Mol Cell Biol. 2020; 21: 24Crossref Scopus (27) Google Scholar). The above combined results suggest that actin cytoskeletal regulation via MIHIR interactions may be a major function of PGRMC1. The MIHIR was inserted into the Cytb5 fold in MAPR proteins (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar), forming a continuous surface with the heme-binding pocket (Figs. 2B and 2C), so we may predict some interrelationship between MIHIR activity and heme occupancy. Such cytoskeletal interactions could be related to the endothelial-mesenchymal transition (EMT) associated with gastrulation (Fig. 2B), as well as the functional changes to ESCs during decidualization (1Salsano S. González-Martín R. Quiñonero A. López-Martín S. Gómez-Escribano A.P. Pérez-Debén S. et al.Novel non-classic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualization.Fertil Steril. 2020; 113: 1050-1066Abstract Full Text Full Text PDF Scopus (17) Google Scholar). A working hypothesis is that altered actin cytoskeleton of EMT and decidualization both involve dynamically regulated phosphorylation of Y139 and/or Y181, which were acquired in evolution concomitantly with the gastrulation organizer, as well as the associated T178 and S181 residues of bilaterian animals. An additional proline-rich SH3-target motif centered at P64 was acquired by the last amniotic common ancestor, which developed the terrestrial vertebrate amniotic egg (Fig. 2B) (2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar). Protein interactions with SH3 domain proteins are potentially sterically regulated by adjacent S54 phosphorylation in mammals (Fig. 2B) and S57 in primates (not shown). PGRMC1 probably exerts broader influence than just altering actin cytoskeleton and mitochondrial function and metabolism. It also inhabits multiple subcellular locations including plasma membrane, nucleus/nucleolus, endoplasmic reticulum, extracellular, mitochondria and mitotic chromosome kinetochores (from where it could conceivably direct formation of the contractile actin ring) (1Salsano S. González-Martín R. Quiñonero A. López-Martín S. Gómez-Escribano A.P. Pérez-Debén S. et al.Novel non-classic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualization.Fertil Steril. 2020; 113: 1050-1066Abstract Full Text Full Text PDF Scopus (17) Google Scholar, 2Hehenberger E, Eitel M, Fortunato SAV, Miller DJ, Keeling PJ, Cahill MA. Early eukaryotic origins and metazoan elaboration of MAPR family proteins. Mol Phylogenet Evol 2020;148:106814.Google Scholar). Mutational manipulation of the Y180 motif affected the abundance of hundreds of cellular proteins that induced altered cell morphology, migration, glycolytic metabolism, and mitochondrial form and function. The mutations each induced specific and highly disparate states of epigenetic CpG genomic methylation, suggesting that many of the large biological effects could be due to pleiotropic alteration of gene expression across large genomic regions (4Thejer B.M. Adhikary P.P. Kaur A. Teakel S.L. van Oosterum A. Seth I. et al.PGRMC1 phosphorylation affects cell shape, motility, glycolysis, mitochondrial form and function, and tumor growth.BMC Mol Cell Biol. 2020; 21: 24Crossref Scopus (27) Google Scholar). Such changes could be expected if PGRMC1 phosphorylation sites are required to maintain cell differentiation status, such as is initiated by gastrulation organizer activity. Decidualization occurs in both marsupial and placental mammals, both of which have S54 near the proline-rich SH3-target motif (Fig. 2B). It is unknown whether monotreme PGRMC1 contains S54, or indeed whether the SH3 motif is even relevant to P4-induced signaling. PGRMC1 mediates P4 responsiveness of both Sertoli and granulosa feeder cells of male and female germline cells, respectively. It will also be interesting to characterize in more detail the role of PGRMC1-like proteins in germline maintenance and perhaps segregation, and even whether any motifs shown in Figure 2B are related to the evolution of marsupial and placental mammalian implantation and gestation, including the decidualization process. Other important questions include how P4 modulates PGRMC1 function, and indeed which of the multiple PGRMC1 functions are P4 dependent and independent. For that, we will need to map the pathways and processes directed by PGRMC1 and the closely related PGRMC2 (3Galmozzi A. Kok B.P. Kim A.S. Montenegro-Burke J.R. Lee J.Y. Spreafico R. et al.PGRMC2 is an intracellular haem chaperone critical for adipocyte function.Nature. 2019; 576: 138-142Crossref PubMed Scopus (57) Google Scholar), especially those modulated by progestogens and differential heme binding. Studies such as the one by Salsano et al. (1Salsano S. González-Martín R. Quiñonero A. López-Martín S. Gómez-Escribano A.P. Pérez-Debén S. et al.Novel non-classic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualization.Fertil Steril. 2020; 113: 1050-1066Abstract Full Text Full Text PDF Scopus (17) Google Scholar) pave a roadway toward that goal. Novel nonclassic progesterone receptor PGRMC1 pulldown-precipitated proteins reveal a key role during human decidualizationFertility and SterilityVol. 113Issue 5PreviewTo investigate PGRMC1-precipitating proteins in human endometrial stromal cells (ESC) to understand its role during in vitro decidualization. Full-Text PDF
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