Rab3A and Rab3B carboxy-terminal peptides are both potent and specific inhibitors of prolactin release by rat cultured anterior pituitary cells.
Chimeric polypeptides composed of the homeodomain of Antennapedia and of the C-terminus of several low molecular weight GTP-binding proteins of the rab family have been found to translocate through the membrane of cells in culture and to accumulate in the cytoplasm and nucleus. We have used these chimeric peptides to study, in intact endocrine cells, a putative role for the C-terminal domain of rab proteins in the exocytotic process. We show that the internalization of 33- and 32-amino acid polypeptides corresponding to the C-terminal domains of rab3A and rab3B blocks calcium-triggered PRL release from adult rat anterior pituitary cells maintained in primary culture. This effect is specific to rab3 since it is not observed after internalization of either rab1 or rab2 C-terminal peptides. In addition, we demonstrate that this inhibition does not require the geranylgeranylation of the internalized C-termini. As rab3B normally shows a permissive effect on exocytosis in PRL-secreting cells, we suggest that the C-terminal domains of rab3A and rab3B contain structural elements that compete with endogenous rab3 necessary for calcium-induced exocytosis.
CNRS URA 1414, Ecole Normale Supérieure, Paris, France.
F
F
Perez
P M
PM
Lledo
D
D
Karagogeos
J D
JD
Vincent
A
A
Prochiantz
J
J
Ayala
D000595:Amino Acid Sequence; D000818:Animals; D051943:Antennapedia Homeodomain Protein; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005089:Exocytosis / Q000187:drug effects; D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018398:Homeodomain Proteins; D015759:Ionomycin / Q000037:antagonists & inhibitors; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010446:Peptide Fragments / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D017368:Protein Prenylation; D011499:Protein Processing, Post-Translational; D051381:Rats; D017208:Rats, Wistar; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000494:pharmacology; D012636:Secretory Rate / Q000187:drug effects; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D020692:rab3 GTP-Binding Proteins
D051943:Antennapedia Homeodomain Protein; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D015759:Ionomycin; D011388:Prolactin; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins