Open AccessImmunofluorescence microscopy of SNAP23 in human skeletal muscle reveals colocalization with plasma membrane, lipid droplets, and mitochondria
Author(s) -
Strauss Juliette A.,
Shaw Christopher S.,
Bradley Helen,
Wilson Oliver J.,
Dorval Thierry,
Pilling James,
Wagenmakers Anton J. M.
Publication year - 2016
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.12662
Subject(s) - colocalization , skeletal muscle , lipid droplet , snap23 , biology , microbiology and biotechnology , immunoelectron microscopy , subcellular localization , dystrophin , biochemistry , chemistry , membrane protein , membrane , cytoplasm , anatomy , vesicle associated membrane protein 8 , immunohistochemistry , immunology
Synaptosomal‐associated protein 23 ( SNAP 23) is a SNARE protein expressed abundantly in human skeletal muscle. Its established role is to mediate insulin‐stimulated docking and fusion of glucose transporter 4 ( GLUT 4) with the plasma membrane. Recent in vitro research has proposed that SNAP 23 may also play a role in the fusion of growing lipid droplets ( LD s) and the channeling of LD ‐derived fatty acids ( FA s) into neighboring mitochondria for β ‐oxidation. This study investigates the subcellular distribution of SNAP 23 in human skeletal muscle using immunofluorescence microscopy to confirm that SNAP 23 localization supports the three proposed metabolic roles. Percutaneous biopsies were obtained from the m. vastus lateralis of six lean, healthy males in the rested, overnight fasted state. Cryosections were stained with antibodies targeting SNAP 23, the mitochondrial marker cytochrome c oxidase and the plasma membrane marker dystrophin, whereas intramuscular LD s were stained using the neutral lipid dye oil red O. SNAP 23 displayed areas of intense punctate staining in the intracellular regions of all muscle fibers and continuous intense staining in peripheral regions of the cell. Quantitation of confocal microscopy images showed colocalization of SNAP 23 with the plasma membrane marker dystrophin (Pearson's correlation coefficient r = 0.50 ± 0.01). The intense punctate intracellular staining colocalized primarily with the mitochondrial marker cytochrome C oxidase ( r = 0.50 ± 0.012) and to a lesser extent with LD s ( r = 0.21 ± 0.01) visualized with oil red O. We conclude that the observed subcellular distribution of SNAP 23 in human skeletal muscle supports the three aforementioned metabolic roles.