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Ca(2+)-triggered exocytosis was studied in single rat melanotrophs and bovine chromaffin cells by capacitance measurements. Sustained exocytosis required MgATP, but even in the absence of MgATP, Ca2+ could trigger exocytosis of 2700 granules in a typical melanotroph and of 840 granules in a chromaffin cell. Granules undergoing ATP-independent exocytosis(More)
The homotypic fusion of sea urchin egg cortical vesicles (CV) is a system in which to correlate the biochemistry and physiology of membrane fusion. Homologues of vesicle-associated membrane protein (VAMP), syntaxin, and SNAP-25 were identified in CV membranes. A VAMP and syntaxin immunoreactive band at a higher apparent molecular mass (approximately 70 kDa)(More)
The process of regulated exocytosis is defined by the Ca2+-triggered fusion of two apposed membranes, enabling the release of vesicular contents. This fusion step involves a number of energetically complex steps and requires both protein and lipid membrane components. The role of cholesterol has been investigated using isolated release-ready native cortical(More)
Exocytosis is a highly conserved and essential process. Although numerous proteins are involved throughout the exocytotic process, the defining membrane fusion step appears to occur through a lipid-dominated mechanism. Here we review and integrate the current literature on protein and lipid roles in exocytosis, with emphasis on the multiple roles of(More)
Cortical vesicles (CV) possess components critical to the mechanism of exocytosis. The homotypic fusion of CV centrifuged or settled into contact has a sigmoidal Ca2+ activity curve comparable to exocytosis (CV-PM fusion). Here we show that Sr2+ and Ba2+ also trigger CV-CV fusion, and agents affecting different steps of exocytotic fusion block Ca2+, Sr2+,(More)
The Ca(2+)-triggered merger of two apposed membranes is the defining step of regulated exocytosis. CHOL is required at critical levels in secretory vesicle membranes to enable efficient, native membrane fusion: CHOL-sphingomyelin enriched microdomains organize the site and regulate fusion efficiency, and CHOL directly supports the capacity for membrane(More)
The recently developed MALDI TOF-TOF instrument yields relatively complex but interpretable fragmentation spectra. When coupled with a straightforward sequence extension algorithm, it is possible to develop complete peptide sequences de novo from the spectra. This approach has been applied to a set of peptides derived from typtic digestion of(More)
Cortical vesicles (CV) possess components critical to the mechanism of exocytosis. The homotypic fusion of CV centrifuged or settled into contact has a sigmoidal Ca 2 ϩ activity curve comparable to exocytosis (CV–PM fusion). Here we show that Sr 2 ϩ and Ba 2 ϩ also trigger CV–CV fusion, and agents affecting different steps of exocytotic fusion block Ca 2 ϩ(More)
This Special Issue (SI) of Cell Calcium focuses on regulated exocytosis, a recent evolutionary invention of eukaryotic cells. This essential cellular process consists of several stages: (i) the delivery of membrane bound vesicles to specific plasma membrane sites, (ii) where the merger between the vesicle and the plasma membranes occurs, (iii) leading to(More)