Involvement of caveolin-1 in meiotic cell-cycle progression in Caenorhabditis elegans

Abstract

mall invaginations called caveolae are present on the surface of many cells and are a form of glycosphingolipid-and cholesterol-enriched microdomains or rafts in the plasma membrane 1,2 . The main component of the caveolar coat is caveolin-1 (refs 3,4), a membrane protein of relative molecular mass (M r ) 21,000 (21K), which binds cholesterol 5 and can form highmolecular-mass homo-oligomers resistant to sodium dodecyl sulphate (SDS) 6,7 . Caveolin-1 has been implicated in signal transduction, but its function remains unclear; whereas overactivation of the p42/44 MAP-kinase cascade was observed after downregulation of caveolin-1 (ref. 8), integrin-mediated activation of the Ras/ extracellular-signal-regulated kinase (ERK) pathway 9 or conversion of prostate cancer cells to an androgen-insensitive phenotype 10 required expression of caveolin-1. To resolve the function of caveolin-1 in intact animals, we analysed caveolin-1 and glycosphingolipid/cholesterol-enriched rafts during the development of the nematode Caenorhabditis elegans. We show that C. elegans caveolin-1 (CAV-1) is expressed in the adult germ line and during embryonic development, and that CAV-1 is essential for Ras/MAP-kinase-dependent progression through the meiotic cell cycle. The function of CAV-1 is dependent on its association with cholesterol-rich membrane microdomains, providing a link between the membrane composition of germ cells and meiotic progression. Our results demonstrate that caveolin-1 and cholesterol-rich microdomains have an essential role in signal transduction in vivo and suggest a model for meiotic progression in the C. elegans germ line.C. elegans has two caveolin-like genes, encoding CAV-1 and CAV-2 (ref. 11, and J.S. and T.V.K., unpublished). CAV-1 is about 67% similar and 37% identical to the mammalian caveolins-1 and -3 respectively over their entire length, whereas CAV-2 is a more distantly related member of the caveolin family 11 . Polyclonal antibodies produced against the carboxy-terminal peptide of CAV-1 recognize a single band of about 31K in western blots of C. elegans lysates (Fig. 1a). CAV-1 is expressed at low levels in adults (Fig. 1b), where it is found in germ cells (Fig. 1d). The protein is strongly expressed in most, if not all, cells throughout embryonic development (Fig. 1b,e,f). In late embryos and L1 larvae, cav-1 expression becomes restricted to the nervous system and diminishes during larval development (data not shown).The function of CAV-1 in C. elegans was studied by RNA interference (RNAi) 12 , a powerful method of obtaining phenocopies of C. elegans mutants by RNA injection into hermaphrodites. Treatment with RNAi for cav-1, after which CAV-1 is no longer detectable (data not shown), results in a burst of egg laying by the injected hermaphrodite. One hundred and twelve eggs (s.d. = 3) were laid by injected hermaphrodites (n = 30) within 36 h after injection of late L4 larvae, compared with 46 eggs laid (s.d. = 2) by control animals (n = 30). Behaviour, morphology and lifespan of injected hermaphrodi...

Muscular dystrophy associated mutations in caveolin-1 induce neurotransmission and locomotion defects in Caenorhabditis elegans

“…Of particular interest was the punctate nature of labelling which is most obvious in the VNC, this staining suggests possible localisation to synapses. A similar expression pattern with an anti-CAV-1 antibody was observed by Scheel (1999).…”

“…The CAV-1 protein is equally similar to both caveolin-1 and caveolin-3 from mammals. Previous results (Scheel et al 1999) showed that cav-1 is expressed predominantly in the nervous system in adult worms; however, no neuronal function has been elucidated. To investigate the role of cav-1, we used fluorescently tagged proteins to elucidate the localisation of CAV-1.…”

Stimulation of Xenopus laevis Oocyte Maturation by Methyl-β-Cyclodextrin1

“…Although membrane cholesterol and the effects of cholesterol depletion have not yet been tested in mammalian oocytes, caveolin and LDM may play a general role in gamete development and function. Caveolin-1 has been reported to be involved in meiotic cell cycle progression in the nematode Caenorhabditis elegans as indicated by RNA interference [40]. Ablation of caveolin-1 by RNA interference resulted in increased germ cell progression through meiotic development and increased egg laying by the injected hermaphrodite.…”

Caveolin-1-deficient Mice Show Accelerated Mammary Gland Development During Pregnancy, Premature Lactation, and Hyperactivation of the Jak-2/STAT5a Signaling Cascade

“…Similarly, antisense-mediated ablation of Cav-1 expression in NIH 3T3 cells causes sustained hyperactivation of the Ras-p42/44 MAPK cascade (Galbiati et al, 1998). Finally, RNA interference-based ablation of Cav-1 in Caenorhabditis elegans leads to progression of the meiotic cell cycle, a phenotype that mirrors that of Ras activation (Scheel et al, 1999).…”