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Expression and insulin-regulated distribution of caveolin in skeletal muscle. Caveolin does not colocalize with GLUT4 in intracellular membranes.

Authors
  • Muñoz, P
  • Mora, S
  • Sevilla, L
  • Kaliman, P
  • Tomàs, E
  • Gumà, A
  • Testar, X
  • Palacín, M
  • Zorzano, A
Type
Published Article
Journal
Journal of Biological Chemistry
Publisher
American Society for Biochemistry & Molecular Biology (ASBMB)
Publication Date
Apr 05, 1996
Volume
271
Issue
14
Pages
8133–8139
Identifiers
PMID: 8626501
Source
Medline
License
Unknown

Abstract

Caveolin is believed to play an important role in sorting processes, vesicular trafficking, transmembrane signaling, and molecular transport across membranes. In this study we have evaluated the expression and distribution of caveolin in skeletal muscle and its interaction with GLUT4 glucose carriers. Caveolin was expressed to substantial levels in muscle and its expression was regulated in muscle; aging and high fat diet enhanced caveolin expression in skeletal muscle and inversely, myogenesis down-regulated caveolin in L6E9 cells. Under fasting conditions, most of caveolin was found in intracellular membranes and the caveolin present in the cell surface was found in both sarcolemma and T-tubules. Insulin administration led to a redistribution of caveolin from intracellular high density membrane fractions to intracellular lighter density fractions and to the cell surface; this pattern of insulin-induced redistribution was different to what was shown by GLUT4. These results suggests that caveolin is a component of an insulin-regulated machinery of vesicular transport in muscle. Quantitative immunoisolation of GLUT4 vesicles obtained from different intracellular GLUT4 populations revealed the absence of caveolin which substantiates the lack of colocalization of intracellular GLUT4 and caveolin. This indicates that caveolin is not involved in intracellular GLUT4 trafficking in skeletal muscle.

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