Dense core secretory vesicles revealed as a dynamic Ca2+ store in neuroendocrine cells with a vesicle-associated membrane protein aequorin chimaera
JOURNAL OF CELL BIOLOGY
Authors: Mitchell, KJ; Pinton, P; Varadi, A; Tacchetti, C; Ainscow, EK; Pozzan, T; Rizzuto, R; Rutter, GA
Abstract
The role of dense core secretory vesicles in the control of cytosolic-free Ca2+ concentrations ([Ca2+](c)) in neuronal and neuroendocrine cells is enigmatic. By constructing a vesicle-associated membrane protein 2-synaptobrevin.aequorin chimera, we show that in clonal pancreatic islet beta -cells: (a) increases in [Ca2+](c) cause a prompt increase in intravesicular-free Ca2+ concentration ([Ca2+](SV)), which is mediated by a P-type Ca2+-ATPase distinct from the sarco(endo) plasmic reticulum Ca2+-ATPase, but which may be related to the PMR1/ATP2C1 family of Ca2+ pumps; (b) steady state Ca2+ concentrations are 3-5-fold lower in secretory vesicles than in the endoplasmic reticulum (ER) or Golgi apparatus, suggesting the existence of tightly bound and more rapidly exchanging pools of Ca2+; (C) inositol (1,4,5) trisphosphate has no impact on [Ca2+](SV) in intact or permeabilized cells; and (d) ryanodine receptor (RyR) activation with caffeine or 4-chloro-3-ethylphenol in intact cells, or cyclic ADPribose in permeabilized cells, causes a dramatic fall in [Ca2+](SV). Thus, secretory vesicles represent a dynamic Ca2+ store in neuroendocrine cells, whose characteristics are in part distinct from the ER/Golgi apparatus. The presence of RyRs on secretory vesicles suggests that local Ca2+-induced Ca2+ release from vesicles docked at the plasma membrane could participate in triggering exocytosis.
Altered levels of focal adhesion and extracellular matrix-receptor interacting proteins were identified in Hailey-Hailey disease by quantitative iTRAQ proteome analysis
JOURNAL OF CELLULAR BIOCHEMISTRY
Authors: Zhang, Dingwei; Huo, Jia; Li, Ruilian; Zhang, Yanfei; Wang, Zhenghui; Li, Xiaoli
Abstract
Benign chronic familial pemphigus or Hailey-Hailey disease (HHD, OMIM 169600) is a rare, autosomal dominant blistering skin disorder characterized by suprabasal cell separation (acantholysis) of the epidermis. To date, the proteomic changes in skin lesions from HHD patients has not been reported yet. In this study, a sample of skin lesions from HHD patients was collected for isobaric tags for relative and absolute quantitation to analyze proteome changes compared with unaffected individuals. The 134 differentially expressed proteins were assigned to at least one Gene Ontology term, and 123 annotated proteins with significant matches were assigned to 187 known metabolic or signaling pathways listed in the Kyoto Encyclopedia of Genes and Genomes. Most of the altered proteins in skin lesions of HHD patients were enriched in pathways involved in the PI3K-Akt signaling, focal adhesion, extracellular matrix (ECM)-receptor interaction, and protein digestion and absorption, such as collagen family members, microfibril-associated glycoprotein 4 and plakophilin. The changes of proteins related to cell adhesion, ECM-receptor interaction, and protein folding and glycosylation suggested that strategy targeted to alter cell junction and extracellular microenvironment might provide a potential treatment for HHD.