A dual function for Munc-18 in exocytosis of PC12 cells.
Munc-18 interacts with the SNARE protein syntaxin and is supposed to influence transmitter release by controlling the formation of exocytosis-relevant SNARE complexes. Here, we used combined biochemical and physiological analyses to study the role of the Munc-18/syntaxin interaction in large dense core vesicle (LDCV) exocytosis of neuroendocrine PC12 cells. We compared two Munc-18 mutants carrying mutations in the syntaxin-binding region and show that Munc-18's membrane association depends on direct binding to syntaxin. The data suggest that perturbation of syntaxin binding inhibits neurotransmitter release upstream of the individual fusion event implying an essential role of the Munc-18/syntaxin complex leading to exocytosis. Furthermore, we show that a Munc-18 mutant lacking any syntaxin binding has a stimulatory effect on secretion, and provide evidence that the Munc-18/Mint1 interaction may constitute a second pathway for Munc-18 to regulate exocytosis. We propose that Munc-18 represents a dynamic link between syntaxin-related and Mint1-related mechanisms, both involved in the control of LDCV exocytosis in neuroendocrine cells.
Schütz
Dagmar
D
Max-Planck-Institute for Biophysical Chemistry, Department of Neurobiology, Am Fassberg 11, 37077 Göttingen, Germany.
Zilly
Felipe
F
Lang
Thorsten
T
Jahn
Reinhard
R
Bruns
Dieter
D
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics; D008565:Membrane Proteins; D051938:Munc18 Proteins; D016296:Mutagenesis; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism*; D009474:Neurons / Q000502:physiology*; D016716:PC12 Cells; D011485:Protein Binding; D051381:Rats; D013572:Synaptic Vesicles / Q000378:metabolism; D050827:Syntaxin 1; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics* / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000954:Antigens, Surface; C513071:Apba1 protein, rat; D008565:Membrane Proteins; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins