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Regulation of the Cop9 Signalosome (CSN) during adipocyte hyperplasia
Author(s) -
Ferguson Bradley S,
Fernandes Karishma M,
Auld Corinth A,
Morrison Ron F
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a703-c
Subject(s) - adipocyte , microbiology and biotechnology , cytosol , biology , cell growth , cop9 signalosome , biochemistry , adipose tissue , enzyme , protease , peptide hydrolases
Knowledge concerning mechanisms that control proliferation and differentiation of preadipocytes is essential to our understanding of adipocyte hyperplasia and the development of childhood obesity. The CSN complex, originally discovered in Arabidopsis, was recently found in humans and proposed to function in signaling cascades essential for development. Using 3T3‐L1 preadipocytes as a model of adipocyte hyperplasia, we investigated the regulation of the CSN complex during states of growth arrest, proliferation, and differentiation. We report that all eight known subunits of the CSN complex are abundantly expressed in this murine cell line with individual masses ranging from 57 (CSN1) to 22 kDa (CSN8) under denaturing conditions. Fractionating cellular extracts under non‐denaturing conditions using glycerol gradient centrifugation followed by SDS‐PAGE immunoblotting revealed a 500 kDa complex composed of CSN subunits. Immunoblotting whole cell lysates over the course of differentiation demonstrated differential regulation with CSN6 and CSN8 decreasing and CSN7 increasing in protein abundance with acquisition of the adipocyte phenotype. We also observed that while CSN7 is predominantly localized to the nucleus, other CSN subunits were observed in both cytosolic and nuclear compartments. Treating preadipocytes with curcumin, a CSN kinase inhibitor, blocked proliferation resulting in elevated levels of p27 and G1 arrest. These data demonstrate novel regulation of the CSN complex during adipocyte development and suggest a functional role in mediating adipocyte hyperplasia. Work supported by American Heart Assoc (0265418U) and NIH (1R21DK072067‐01).