Lipoprotein Lipase and Leptin Are Accumulated in Different Secretory Compartments in Rat Adipocytes

Adipose cells produce and secrete several physiologically important proteins, such as lipoprotein lipase (LPL), leptin, adipsin, Acrp30, etc. However, secretory pathways in adipocytes have not been characterized, and vesicular carriers responsible for the accumulation and transport of secreted prote...

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Bibliographic Details
Published inThe Journal of biological chemistry Vol. 276; no. 38; pp. 35990 - 35994
Main Authors Roh, Cecilia, Roduit, Raphael, Thorens, Bernard, Fried, Susan, Kandror, Konstantin V.
Format Journal Article
LanguageEnglish
Published United States Elsevier Inc 21.09.2001
American Society for Biochemistry and Molecular Biology
Subjects
Adipocytes - enzymology
Adipocytes - metabolism
Animals
Cell Compartmentation
In Vitro Techniques
Leptin - metabolism
Lipoprotein Lipase - metabolism
Male
Microscopy, Confocal
Microscopy, Fluorescence
Rats
Rats, Sprague-Dawley
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Summary:Adipose cells produce and secrete several physiologically important proteins, such as lipoprotein lipase (LPL), leptin, adipsin, Acrp30, etc. However, secretory pathways in adipocytes have not been characterized, and vesicular carriers responsible for the accumulation and transport of secreted proteins have not been identified. We have compared the intracellular localization of two proteins secreted from adipose cells: leptin and LPL. Adipocytes accumulate large amounts of both proteins, suggesting that neither of them is targeted to the constitutive secretory pathway. By means of velocity centrifugation in sucrose gradients, equilibrium density centrifugation in iodixanol gradients, and immunofluorescence confocal microscopy, we determined that LPL and leptin were localized in different membrane structures. LPL was found mainly in the endoplasmic reticulum with a small pool being present in low density membrane vesicles that may represent a secretory compartment in adipose cells. Virtually all intracellular leptin was localized in these low density secretory vesicles. Insulin-sensitive Glut4 vesicles did not contain either LPL or leptin. Thus, secretion from adipose cells is controlled both at the exit from the endoplasmic reticulum as well as at the level of “downstream” secretory vesicles.
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
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ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M102791200