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Mutational analysis of cysteine-string protein function in insulin exocytosis

Zhang, H.
Chamberlain, L. H.
Burgoyne, R. D.
Published in Journal of Cell Science. 1999, vol. 112, no. 9, p. 1345-1351
Abstract Cysteine-string proteins (Csps) are vesicle proteins involved in neurotransmission. They contain at least four domains: an N-terminal J-domain which can interact with the chaperone Hsc70, an adjacent linker region, the defining cysteine rich domain and a variable C terminus. As the relevance of these domains for the function of Csps in exocytosis is unknown, we have performed a mutational analysis of Csp domains using insulin release by large dense core vesicles (LDCVs) as a model of regulated exocytosis. All mutants were apparently palmitoylated and their subcellular distribution was similar to endogenous Csp. Point mutations within the highly conserved HPD motif of the J-domain abolished activation of Hsc70. However, these mutations altered the effect of Csp on exocytosis only after additional truncation of the extreme C terminus as found in the Csp splice variant Csp2. Furthermore, the strikingly conserved linker region adjacent to the J-domain was important for Csp function in exocytosis, but not for the activation of Hsc70 ATPase. The effects of Csp wild-type or mutants were preserved in permeabilized cells excluding an effect on transmembrane ion fluxes. These observations demonstrate a functional difference between the two isoforms and suggest a role for the J-domain co-chaperone function as well as for the newly defined linker region in LDCV exocytosis.
Keywords Cells, CulturedExocytosis/ physiologyHSP40 Heat-Shock ProteinsHumansInsulin/ secretionMembrane Proteins/ geneticsMutagenesis, Site-DirectedNerve Tissue Proteins/ geneticsPoint MutationSubcellular Fractions/chemistry
PMID: 10194413
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ZHANG, H. et al. Mutational analysis of cysteine-string protein function in insulin exocytosis. In: Journal of Cell Science, 1999, vol. 112, n° 9, p. 1345-1351. https://archive-ouverte.unige.ch/unige:7715

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Deposited on : 2010-06-21

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