Ca<sup>2+</sup>-independent insulin exocytosis induced by alpha-latrotoxin requires latrophilin, a G protein-coupled receptor

Lang, Jochen; Ushkaryov, Y; Grasso, A; Wollheim, Claes

doi:10.1093/emboj/17.3.648

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Title		Ca²⁺-independent insulin exocytosis induced by alpha-latrotoxin requires latrophilin, a G protein-coupled receptor
Authors		Lang, Jochen Ushkaryov, Y Grasso, A Wollheim, Claes
Published in		EMBO Journal. 1998, vol. 17, no. 3, p. 648-57
Abstract		alpha-Latrotoxin (alpha-LTX) induces exocytosis of small synaptic vesicles (SSVs) in neuronal cells both by a calcium-independent mechanism and by opening cation-permeable pores. Since the basic molecular events regulating exocytosis in neurons and endocrine cells may be similar, we have used the exocytosis of insulin-containing large dense core vesicles (LDCVs) as a model system. In primary pancreatic beta-cells and in the derived cell lines INS-1 and MIN6, alpha-LTX increased insulin release in the absence of extracellular calcium, but the insulin-secreting cell lines HIT-T15 and RINm5F were unresponsive. alpha-LTX did not alter membrane potential or cytosolic calcium, and its stimulatory effect on exocytosis was still observed in pre-permeabilized INS-1 cells kept at 0.1 microM Ca2+. Consequently, pore formation or ion fluxes induced by alpha-LTX could be excluded. The Ca2+-independent alpha-LTX-binding protein, latrophilin, is a novel member of the secretin family of G protein-coupled receptors (GPCR). Sensitivity to alpha-LTX correlated with expression of latrophilin, but not with synaptotagmin I or neurexin Ialpha expression. Moreover, transient expression of latrophilin in HIT-T15 cells conferred alpha-LTX-induced exocytosis. Our results indicate that direct stimulation of exocytosis by a GPCR mediates the Ca2+-independent effects of alpha-LTX in the absence of altered ion fluxes. Therefore, direct regulation by receptor-activated heterotrimeric G proteins constitutes an important feature of the endocrine exocytosis of insulin-containing LDCVs and may also apply to SSV exocytosis in neurons.
Keywords		Animals — Bacterial Toxins/pharmacology — Calcium/pharmacology — Calcium-Binding Proteins — Cell Line — Cell Membrane/drug effects/physiology — Cell Membrane Permeability/drug effects — Cytosol/chemistry/drug effects — Exocytosis/drug effects/physiology — GTP-Binding Proteins/metabolism — Gene Expression — Glycoproteins — Hemolysin Proteins/pharmacology — Insulin/secretion — Islets of Langerhans/metabolism/secretion — Membrane Glycoproteins/genetics — Membrane Potentials/drug effects — Nerve Tissue Proteins/genetics — Neuropeptides — Protein Binding — Receptors, Cell Surface/metabolism — Receptors, Peptide/genetics/metabolism — Spider Venoms/chemistry/metabolism/pharmacology — Staphylococcus aureus/chemistry — Synaptotagmin I — Synaptotagmins
Identifiers		DOI: 10.1093/emboj/17.3.648 PMID: 9450990
Full text		Article (Published version) (542 Kb) - Free access
Structures		Faculté de médecine / Section de médecine clinique / Département de médecine
Citation (ISO format)		LANG, Jochen et al. Ca²⁺-independent insulin exocytosis induced by alpha-latrotoxin requires latrophilin, a G protein-coupled receptor. In: EMBO Journal, 1998, vol. 17, n° 3, p. 648-57. doi: 10.1093/emboj/17.3.648 https://archive-ouverte.unige.ch/unige:35649