RasGRP3 mediates phorbol ester-induced, protein kinase C-independent exocytosis.
Phorbol esters are involved in neurotransmitter release and hormone secretion via activation of protein kinase C (PKC). In addition, it has been recently reported to enhance neurotransmitter release in a PKC-independent manner. However, the exocytotic machinery is not fully clarified. Nowadays members of the RasGRP family are being identified as novel molecules binding to diacylglycerol and calcium, representing a new class of guanine nucleotide exchange factor that activates small GTPases including Ras and Rap1. In the present study, we demonstrated that RasGRP3 is expressed in endocrine tissues and mediates phorbol ester-induced exocytosis. Furthermore, the effects were partially blocked by PKC inhibitor but not mitogen-activated protein kinase kinase inhibitor, although both significantly suppressed the phorbol ester-induced phosphorylation of extracellular signal-regulated kinase 1/2. These results indicate that RasGRP3 is implicated in phorbol ester-induced, PKC-independent exocytosis.
Ozaki
Nobuaki
N
Department of Metabolic Disease, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. n-ozaki@med.nagoya-u.ac.jp
Miura
Yoshitaka
Y
Yamada
Tsutomu
T
Kato
Yoshiro
Y
Oiso
Yutaka
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016716:PC12 Cells; D010703:Phorbol Esters / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats
D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D010703:Phorbol Esters; C491789:Rasgrp1 protein, rat; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium