Two Compartments for Insulin-Stimulated Exocytosis in 3t3-L1 Adipocytes Defined by Endogenous Acrp30 and Glut4

Two Compartments for Insulin-Stimulated Exocytosis in 3t3-L1 Adipocytes Defined by Endogenous... Insulin stimulates adipose cells both to secrete proteins and to translocate the GLUT4 glucose transporter from an intracellular compartment to the plasma membrane. We demonstrate that whereas insulin stimulation of 3T3-L1 adipocytes has no effect on secretion of the α3 chain of type VI collagen, secretion of the protein hormone adipocyte complement related protein of 30 kD (ACRP30) is markedly enhanced. Like GLUT4, regulated exocytosis of ACRP30 appears to require phosphatidylinositol-3-kinase activity, since insulin-stimulated ACRP30 secretion is blocked by pharmacologic inhibitors of this enzyme. Thus, 3T3-L1 adipocytes possess a regulated secretory compartment containing ACRP30. Whether GLUT4 recycles to such a compartment has been controversial. We present deconvolution immunofluorescence microscopy data demonstrating that the subcellular distributions of ACRP30 and GLUT4 are distinct and nonoverlapping; in contrast, those of GLUT4 and the transferrin receptor overlap. Together with supporting evidence that GLUT4 does not recycle to a secretory compartment via the trans-Golgi network, we conclude that there are at least two compartments that undergo insulin-stimulated exocytosis in 3T3-L1 adipocytes: one for ACRP30 secretion and one for GLUT4 translocation. exocytosis monosaccharide transport proteins insulin adipose tissue secretion Footnotes 1.used in this paper: ACRP30, adipocyte complement related protein of 30 kD; GLUT, glucose transporter; PI-3 kinase, phosphatidylinositol-3-kinase; TfnR, transferrin receptor Submitted: 23 April 1999 Revision requested 29 June 1999 Accepted: 1 July 1999 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Cell Biology Rockefeller University Press

Two Compartments for Insulin-Stimulated Exocytosis in 3t3-L1 Adipocytes Defined by Endogenous Acrp30 and Glut4

The Journal of Cell Biology, Volume 146 (3): 609 – Aug 9, 1999

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Publisher
Rockefeller University Press
Copyright
© 1999 The Rockefeller University Press
ISSN
0021-9525
eISSN
1540-8140
D.O.I.
10.1083/jcb.146.3.609
Publisher site
See Article on Publisher Site

Abstract

Insulin stimulates adipose cells both to secrete proteins and to translocate the GLUT4 glucose transporter from an intracellular compartment to the plasma membrane. We demonstrate that whereas insulin stimulation of 3T3-L1 adipocytes has no effect on secretion of the α3 chain of type VI collagen, secretion of the protein hormone adipocyte complement related protein of 30 kD (ACRP30) is markedly enhanced. Like GLUT4, regulated exocytosis of ACRP30 appears to require phosphatidylinositol-3-kinase activity, since insulin-stimulated ACRP30 secretion is blocked by pharmacologic inhibitors of this enzyme. Thus, 3T3-L1 adipocytes possess a regulated secretory compartment containing ACRP30. Whether GLUT4 recycles to such a compartment has been controversial. We present deconvolution immunofluorescence microscopy data demonstrating that the subcellular distributions of ACRP30 and GLUT4 are distinct and nonoverlapping; in contrast, those of GLUT4 and the transferrin receptor overlap. Together with supporting evidence that GLUT4 does not recycle to a secretory compartment via the trans-Golgi network, we conclude that there are at least two compartments that undergo insulin-stimulated exocytosis in 3T3-L1 adipocytes: one for ACRP30 secretion and one for GLUT4 translocation. exocytosis monosaccharide transport proteins insulin adipose tissue secretion Footnotes 1.used in this paper: ACRP30, adipocyte complement related protein of 30 kD; GLUT, glucose transporter; PI-3 kinase, phosphatidylinositol-3-kinase; TfnR, transferrin receptor Submitted: 23 April 1999 Revision requested 29 June 1999 Accepted: 1 July 1999

Journal

The Journal of Cell BiologyRockefeller University Press

Published: Aug 9, 1999

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