Avtor/Urednik     Rupnik, Marjan
Naslov     Vloga beljakovine Rab3A pri sekrecijski aktivnosti podganjih melanotrofov
Tip     monografija
Kraj izdaje     Ljubljana
Založnik     Medicinska fakulteta
Leto izdaje     1996
Obseg     str. 63
Jezik     slo
Abstrakt     Rab GTPases regulate specifcity and the speed of intercompartmental membrane vesicle traffic in the course of the biosynthetic and endocytotic pathways. Rab3 proteins are thought to play a key role in the fnal step of the biosynthetic pathway. By now, four Rab3 isofomis were described in the neuroendocrine cells (A, B, C, D), which have almost completely conserved effector domains. Synthetic oligopeptides rab3AL, corresponding to the Rab3 protein effector domain either stimulated or inhibited Ca2+ dependent secretory activity. Thus it is not possible to differentiate the role for particular isoforms on the basis of rab3AL peptide experiments. Rab3 B is a dominant isofomz in the anterior pituitaty cells. The inhibition of Rab3 B gene expression using antisense oligonucleotides against Rab3B mRNA (yielding Rab3 B (-) cells) attenuated Ca2+ dependent exocytosis in rat lactotrophs. In contrary, in Rab3A (-) chromaf?n cells the secretory activity was augmented. The active (GTP) mutant of Rab3A protein (Rab3 A Q8l L) was inhibitory for Ca2+ dependent secretoiy activity. In rat melanotrophs both Rab3 isoforms, Rab3A and Rab3B are expressed in abundance. The aim of our study was to determine which of the present isoforms is functionally releavant in Ca2+ dependent secretion of single rat melanotroph cell. And secondly, whether its action is stimulatory or inhibitozy. Melanotrophs were prepared as a primary cell culture. Whole-cell patch-clamp was used to measure membrane capacitance, a useful measure of cell surface area. Antisense oligonucleotides and recombinant proteins were microinjected prior to electrophysiological experiment. The microinjection of Rab3A antisense oligonucleotides, but not Rab3B, completely abolished Ca2+ induced secretory activity. Active Rab3A mutant (Rab3A QBl L) induced further enhancement of the secretory activity. (Abstract truncated at 2000 character)
Deskriptorji     PITUITARY GLAND
CALCIUM
G-PROTEINS
MUTATION
RATS, WISTAR
GTP PHOSPHOHYDROLASE
PATCH-CLAMP TECHNIQUES
CELLS, CULTURED
OLIGOPEPTIDES