Portal de Periódicos da CAPES

Zebrafish as a Novel Model System to Study the Function of Caveolae and Caveolin-1 in Organismal Biology

2006; Elsevier BV; Volume: 169; Issue: 6 Linguagem: Inglês

10.2353/ajpath.2006.060923

1525-2191

Philippe G. Frank, Michael P. Lisanti,

RNA Research and Splicing

Caveolin-1 (Cav-1) was first identified as a marker protein for the purification of caveolae organelles.1Glenney JRJ Soppet D Sequence and expression of caveolin, a protein component of caveolae plasma membrane domains phosphorylated on tyrosine in Rous sarcoma virus-transformed fibroblasts.Proc Natl Acad Sci USA. 1992; 89: 10517-10521Crossref PubMed Scopus (343) Google Scholar, 2Kurzchalia T Dupree P Parton RG Kellner R Virta H Lehnert M Simons K VIP 21, a 21-kD membrane protein is an integral component of trans-Golgi-network-derived transport vesicles.J Cell Biol. 1992; 118: 1003-1014Crossref PubMed Scopus (465) Google Scholar, 3Rothberg KG Heuser JE Donzell WC Ying YS Glenney JR Anderson RG Caveolin, a protein component of caveolae membrane coats.Cell. 1992; 68: 673-682Abstract Full Text PDF PubMed Scopus (1873) Google Scholar Subsequently, it was later determined that Cav-1 expression is essential for caveolae formation.4Drab M Verkade P Elger M Kasper M Lohn M Lauterbach B Menne J Lindschau C Mende F Luft FC Schedl A Haller H Kurzchalia TV Loss of caveolae, vascular dysfunction, and pulmonary defects in caveolin-1 gene-disrupted mice.Science. 2001; 293: 2449-2452Crossref PubMed Scopus (1318) Google Scholar, 5Razani B Engelman JA Wang XB Schubert W Zhang XL Marks CB Macaluso F Russell RG Li M Pestell RG Di Vizio D Hou Jr, H Kneitz B Lagaud G Christ GJ Edelmann W Lisanti MP Caveolin-1 null mice are viable but show evidence of hyperproliferative and vascular abnormalities.J Biol Chem. 2001; 276: 38121-38138Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar Thus, Cav-1(−/−)-deficient mice morphologically lack caveolae organelles. Surprisingly, these mice are viable and fertile.4Drab M Verkade P Elger M Kasper M Lohn M Lauterbach B Menne J Lindschau C Mende F Luft FC Schedl A Haller H Kurzchalia TV Loss of caveolae, vascular dysfunction, and pulmonary defects in caveolin-1 gene-disrupted mice.Science. 2001; 293: 2449-2452Crossref PubMed Scopus (1318) Google Scholar, 5Razani B Engelman JA Wang XB Schubert W Zhang XL Marks CB Macaluso F Russell RG Li M Pestell RG Di Vizio D Hou Jr, H Kneitz B Lagaud G Christ GJ Edelmann W Lisanti MP Caveolin-1 null mice are viable but show evidence of hyperproliferative and vascular abnormalities.J Biol Chem. 2001; 276: 38121-38138Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar In striking contrast, zebrafish (Danio rerio) lacking Cav-1 display important developmental abnormalities and embryonic lethality. These novel findings by Fang et al are described and highlighted in this issue of The American Journal of Pathology.6Fang P-K Solomon KR Zhuang L Qi M McKee M Freeman MR Yelick PC Caveolin-1α and 1β perform non-redundant roles in early vertebrate development.Am J Pathol. 2006; 169: 2209-2222Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar The gene encoding Cav-1 has the same organization, with three exons and two introns, in human,7Engelman JA Zhang XL Lisanti MP Sequence and detailed organization of the human caveolin-1 and -2 genes located near the D7S522 locus (7q31.1). Methylation of a CpG island in the 5′ promoter region of the caveolin-1 gene in human breast cancer cell lines.FEBS Lett. 1999; 448: 221-230Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar mouse,8Engelman JA Zhang XL Galbiati F Lisanti MP Chromosomal localization, genomic organization, and developmental expression of the murine caveolin gene family (Cav-1, -2, and -3). Cav-1 and Cav-2 genes map to a known tumor suppressor locus (6-A2/7q31).FEBS Lett. 1998; 429: 330-336Abstract Full Text Full Text PDF PubMed Scopus (133) Google Scholar and zebrafish.6Fang P-K Solomon KR Zhuang L Qi M McKee M Freeman MR Yelick PC Caveolin-1α and 1β perform non-redundant roles in early vertebrate development.Am J Pathol. 2006; 169: 2209-2222Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar This suggests an important and conserved role for Cav-1 in whole-organismal biology. In fact, sequence alignment reveals that the Cav-1 protein is highly evolutionarily conserved, from Caenorhabditis elegans to humans (Figure 1). Interestingly, a single Cav-1 gene encodes two protein isoforms that differ slightly, only by their N-terminal sequence.9Scherer PE Tang Z Chun M Sargiacomo M Lodish HF Lisanti MP Caveolin isoforms differ in their N-terminal protein sequence and subcellular distribution. Identification and epitope mapping of an isoform-specific monoclonal antibody probe.J Biol Chem. 1995; 270: 16395-16401Crossref PubMed Scopus (323) Google Scholar More specifically, Cav-1α is a 178-amino acid protein, whereas Cav-1β is 147 amino acids and lacks the first 31 N-terminal residues of Cav-1α. These two Cav-1 isoforms have been shown to be translated from distinct mRNA species.10Kogo H Fujimoto T Caveolin-1 isoforms are encoded by distinct mRNAs. Identification of mouse caveolin-1 mRNA variants caused by alternative transcription initiation and splicing.FEBS Lett. 2000; 465: 119-123Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar Until now, the specific functional role of each Cav-1 isoform had not been clearly defined. Nonetheless, Cav-1α and −1β have different subcellular distributions, as demonstrated by recent studies.9Scherer PE Tang Z Chun M Sargiacomo M Lodish HF Lisanti MP Caveolin isoforms differ in their N-terminal protein sequence and subcellular distribution. Identification and epitope mapping of an isoform-specific monoclonal antibody probe.J Biol Chem. 1995; 270: 16395-16401Crossref PubMed Scopus (323) Google Scholar, 11Kogo H Aiba T Fujimoto T Cell type-specific occurrence of caveolin-1alpha and -1beta in the lung caused by expression of distinct mRNAs.J Biol Chem. 2004; 279: 25574-25581Crossref PubMed Scopus (47) Google Scholar, 12Ramirez MI Pollack L Millien G Cao YX Hinds A Williams MC The alpha-isoform of caveolin-1 is a marker of vasculogenesis in early lung development.J Histochem Cytochem. 2002; 50: 33-42Crossref PubMed Scopus (38) Google Scholar Moreover, Cav-1α has been shown to form caveolae more readily than Cav-1β.13Fujimoto T Kogo H Nomura R Une T Isoforms of caveolin-1 and caveolar structure.J Cell Sci. 2000; 113: 3509-3517PubMed Google Scholar In zebrafish, Cav-1 mRNAs are detected during the very early stages of development. Late in development, the Cav-1α mRNA is the only isoform detectable in intestinal epithelium, whereas both Cav-1α and −1β mRNAs are produced in the heart, pharyngeal vasculature, notochord, somites, skin, and neuromast tissues. Interestingly, these data are similar to those obtained in Xenopus laevis.14Razani B Park DS Miyanaga Y Ghatpande A Cohen J Wang XB Scherer PE Evans T Lisanti MP Molecular cloning and developmental expression of the caveolin gene family in the amphibian Xenopus laevis.Biochemistry. 2002; 41: 7914-7924Crossref PubMed Scopus (24) Google Scholar In the mouse, Cav-1α protein expression is detected early in the embryo (E15).12Ramirez MI Pollack L Millien G Cao YX Hinds A Williams MC The alpha-isoform of caveolin-1 is a marker of vasculogenesis in early lung development.J Histochem Cytochem. 2002; 50: 33-42Crossref PubMed Scopus (38) Google Scholar Maximal expression is observed in the vasculature, the lungs, the kidneys, and the gut. Interestingly, in the lungs, Cav-1α expression first appears in endothelial cells. The importance of Cav-1 in the vasculature has also been highlighted by Bullejos et al, who observed high levels of Cav-1 mRNA in the developing ovaries but not testes.15Bullejos M Bowles J Koopman P Extensive vascularization of developing mouse ovaries revealed by caveolin-1 expression.Dev Dyn. 2002; 225: 95-99Crossref PubMed Scopus (33) Google Scholar This difference is due to the formation of a more dense and more complex vascular network in the ovaries.15Bullejos M Bowles J Koopman P Extensive vascularization of developing mouse ovaries revealed by caveolin-1 expression.Dev Dyn. 2002; 225: 95-99Crossref PubMed Scopus (33) Google Scholar In mice, Cav-1 expression does not appear to be as essential as in zebrafish, since its elimination is not lethal.16Williams TM Lisanti MP The caveolin genes: from cell biology to medicine.Ann Med. 2004; 36: 584-595Crossref PubMed Scopus (315) Google Scholar, 17Cohen AW Hnasko R Schubert W Lisanti MP Role of caveolae and caveolins in health and disease.Physiol Rev. 2004; 84: 1341-1379Crossref PubMed Scopus (742) Google Scholar However, its role in the vasculature and other tissues is clearly important, since its absence has been associated with many disease-related phenotypes, most notably in the lung, vasculature, heart, adipose tissue, and the mammary gland. However, the detailed developmental progression of the Cav-1-deficient mouse embryo has yet to be determined. For example, alterations observed in Cav-1-deficient murine lungs could result from developmental abnormalities. In zebrafish, Cav-1 down-regulation, in the case of both isoforms (Cav-1α and Cav-1β), is associated with important defects occurring by 12 hours after fertilization. This time point is normally associated with a remarkable increase in Cav-1 mRNA levels. As expected, reductions in the Cav-1 protein are also associated with a major reduction in the number of caveolae. One of the first proteins shown to associate with caveolae is actin.18Lisanti MP Scherer PE Vidugiriene J Tang Z Hermanowski-Vosatka A Tu YH Cook RF Sargiacomo M Characterization of caveolin-rich membrane domains isolated from an endothelial-rich source: implications for human disease.J Cell Biol. 1994; 126: 111-126Crossref PubMed Scopus (815) Google Scholar, 19Schnitzer JE Oh P Jacobson BS Dvorak AM Caveolae from luminal plasmalemma of rat lung endothelium: microdomains enriched in caveolin, Ca(2+)-ATPase, and inositol trisphosphate receptor.Proc Natl Acad Sci USA. 1995; 92: 1759-1763Crossref PubMed Scopus (231) Google Scholar This “anchoring” interaction appears to be responsible, at least in part, for the extremely reduced mobility of caveolae at the cell surface.20Thomsen P Roepstorff K Stahlhut M van Deurs B Caveolae are highly immobile plasma membrane microdomains, which are not involved in constitutive endocytic trafficking.Mol Biol Cell. 2002; 13: 238-250Crossref PubMed Scopus (375) Google Scholar In addition, during cellular migration, Cav-1 has been shown to assume a polarized distribution in migrating endothelial cells.21Isshiki M Ando J Yamamoto K Fujita T Ying Y Anderson RG Sites of Ca(2+) wave initiation move with caveolae to the trailing edge of migrating cells.J Cell Sci. 2002; 115: 475-484Crossref PubMed Google Scholar, 22Parat MO Anand-Apte B Fox PL Differential caveolin-1 polarization in endothelial cells during migration in two and three dimensions.Mol Biol Cell. 2003; 14: 3156-3168Crossref PubMed Scopus (126) Google Scholar Moreover, it was also shown that this specific polarization during trans-migration requires the presence of the Tyr14Razani B Park DS Miyanaga Y Ghatpande A Cohen J Wang XB Scherer PE Evans T Lisanti MP Molecular cloning and developmental expression of the caveolin gene family in the amphibian Xenopus laevis.Biochemistry. 2002; 41: 7914-7924Crossref PubMed Scopus (24) Google Scholar residue within Cav-1 for phosphorylation, since the distribution of other forms of Cav-1 (Cav-1α (Y14A) and Cav-1β) are not polarized.22Parat MO Anand-Apte B Fox PL Differential caveolin-1 polarization in endothelial cells during migration in two and three dimensions.Mol Biol Cell. 2003; 14: 3156-3168Crossref PubMed Scopus (126) Google Scholar It is important to note that phosphorylation of Cav-1α at Tyr14Razani B Park DS Miyanaga Y Ghatpande A Cohen J Wang XB Scherer PE Evans T Lisanti MP Molecular cloning and developmental expression of the caveolin gene family in the amphibian Xenopus laevis.Biochemistry. 2002; 41: 7914-7924Crossref PubMed Scopus (24) Google Scholar has been associated with its subcellular localization in close proximity to focal adhesions,23Lee H Volonte D Galbiati F Iyengar P Lublin DM Bregman DB Wilson MT Campos-Gonzalez R Bouzahzah B Pestell RG Scherer PE Lisanti MP Constitutive and growth factor-regulated phosphorylation of caveolin-1 occurs at the same site (Tyr-14) in vivo: identification of a c-Src/Cav-1/Grb7 signaling cassette.Mol Endocrinol. 2000; 14: 1750-1775Crossref PubMed Google Scholar as well as caveolae-mediated endocytosis.24Minshall RD Sessa WC Stan RV Anderson RG Malik AB Caveolin regulation of endothelial function.Am J Physiol. 2003; 285: L1179-L1183Google Scholar Interestingly, in zebrafish, a deficiency in Cav-1α cannot be rescued by a mutant form of Cav-1α (Y14F) that cannot undergo phosphorylation. In addition, Cav-1 deficiency is associated with severe disruption of the actin cytoskeleton. These findings suggest that Cav-1 plays a critical role in cell migration and/or endocytosis in zebrafish. Likewise, overexpression of the full-length Cav-1α isoform could not rescue the phenotype induced by the absence of the Cav-1β isoform, and visa versa. Taken together, these data suggest for the first time that Cav-1α and Cav-1β have nonoverlapping functions and that these differences may be related to the ability of the Cav-1α isoform to undergo tyrosine phosphorylation at residue 14. Replacement of zebrafish Cav-1 by the corresponding human Cav-1 isoform could complement the phenotypes associated with the absence of each isoform. This finding further suggests that the function of the Cav-1 protein is highly conserved throughout evolution. In mammals, however, the absence of Cav-1 may not be as lethal as in zebrafish because of the existence of redundant compensatory mechanisms. Clearly, the mouse and human systems are more complicated than zebrafish. However, the zebrafish model of development will provide, for the first time, a genetically tractable system to perform rapid and detailed mutagenesis of both Cav-1α and Cav-1β isoforms. As such, the zebrafish system is a new experimental tool for investigators to directly dissect the relationship between the primary structure of Cav-1 and its essential developmental and whole organismal functions.