Expression of synaptosomal-associated protein SNAP-25 in endocrine anterior pituitary cells.
A growing body of evidence indicates that the fundamental molecular mechanism of exocytosis in the secretory pathway may be structurally similar in all eukaryotic cells. The synaptosomal-associated protein of 25 kDa (SNAP-25) is a plasma membrane protein involved in regulated exocytosis in neurons. In order to compare exocytotic components in neurons and endocrine cells, we have analyzed the expression of SNAP-25 in the rat anterior pituitary. Western blotting analysis documented the presence of SNAP-25 in anterior pituitary homogenates and cultured anterior pituitary cells. In addition to SNAP-25, other neuronal proteins involved in exocytosis (syntaxin, VAMP/synaptobrevin and Rab3A) were also detected in the anterior pituitary. The specific expression of SNAP-25 mRNA in anterior pituitary cells was also corroborated by Northern analysis. SNAP-25 immunoreactivity was located at the plasma membrane of endocrine anterior pituitary cells. Characteristically, patches of fine punctate deposits exhibited intense SNAP-25 immunoreactivity. Double-labeling immunocytochemistry revealed that SNAP-25 was mainly associated with gonadotroph cell populations. Furthermore, we demonstrate that in the anterior pituitary, SNAP-25 is selectively cleaved by clostridial neurotoxins. In conclusion, our results establish the presence of SNAP-25 in secretory anterior pituitary cells and suggest a potential role of this protein in the secretion of adenohypophysial hormone.
Aguado
F
F
Department de Biologia Cel.lular i Anatomia Patològica, Facultat de Medicina, Universitat de Barcelona, Hospital de Bellvitge, Spain.
Majó
G
G
Ruiz-Montasell
B
B
Canals
J M
JM
Casanova
A
A
Marsal
J
J
Blasi
J
J
D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000378:metabolism; D007124:Immunoenzyme Techniques; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D050825:Synaptosomal-Associated Protein 25; D020692:rab3 GTP-Binding Proteins
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D012333:RNA, Messenger; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins