title: Inhibition of Bufo arenarum oocyte maturation induced by cholesterol depletion by methyl-beta-cyclodextrin. Role of low-density caveolae-like membranes.
abstract: The invaginated structure of caveolae seems to provide an optimal environment for hormone binding leading to oocyte meiotic maturation. We conducted a quantitative analysis of lipids and proteins of detergent-free low-density membranes isolated from Bufo arenarum oocytes and we modulated cellular cholesterol to further understand how these domains perform their regulatory functions in the amphibian system. Light membranes derive from the plasma membrane as suggested by the enrichment in the activity of 5'nucleotidase. Lipid analysis by chromatography techniques revealed that this fraction is enriched in phosphatidylserine and cholesterol and that it evidences an important level of sphingomyelin. The finding of a single 21 kDa caveolin in light membranes indicates the presence of caveolae-like structures in B. arenarum oocytes. In support of this finding, c-Src is significantly associated to this fraction. Cholesterol content of oocytes treated with methyl-beta-cyclodextrin (MbetaCD) decreased when compared to control oocytes. Drug treatment inhibited meiotic maturation in a dose-dependent manner and affected the localization of caveolin and c-Src among membrane fractions. Repletion of cholesterol showed a recovery of the ability of MbetaCD-treated oocytes to mature, particularly at the 25 mM concentration in which reversibility was close to the control level. Results highlight the importance of caveolae-like microdomains for maturation signaling in Bufo oocytes.
authors.affiliation: Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur, Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina.
authors.forename: Jorgelina
authors.initials: J
authors.lastname: Buschiazzo
authors.forename: Ida C
authors.initials: IC
authors.lastname: Bonini
authors.forename: Telma S
authors.initials: TS
authors.lastname: Alonso
mesh_terms: D029845:Amphibian Proteins / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002022:Bufo arenarum; D021941:Caveolae / Q000737:chemistry / Q000378:metabolism*; D022461:Caveolins / Q000737:chemistry / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D008540:Meiosis / Q000187:drug effects* / Q000502:physiology; D009865:Oocytes / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D047392:beta-Cyclodextrins / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D029845:Amphibian Proteins; D022461:Caveolins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D002784:Cholesterol