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J. Biol. Chem., Vol. 281, Issue 33, 23307-23312, August 18, 2006

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Dual Regulation of Rho and Rac by p120 Catenin Controls Adipocyte Plasma Membrane Trafficking^*

June C. Hou, Satoshi Shigematsu, Howard C. Crawford, Panos Z. Anastasiadis^¶, and Jeffrey E. Pessin¹

From the Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794-8651, the Department of Aging Medicine and Geriatrics, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan, and ^¶Mayo Clinic Cancer Center, Jacksonville, Florida 32224

During 3T3L1 adipogenesis there is a marked reduction in -catenin and N-cadherin expression with a relatively small decrease in p120 catenin protein levels. Cell fractionation demonstrated a predominant decrease in the particulate (membrane-bound) pool of p120 catenin with little effect on the soluble pool, resulting in a large redistribution from the plasma membrane to the cytosol. Reexpression of p120 catenin inhibited constitutive (transferrin receptor) and regulated mannose 6-phosphate receptor and GLUT4 trafficking to the plasma membrane. The inhibition of membrane trafficking was specific for p120 catenin function as this could be rescued by co-expression of N-cadherin. Moreover, overexpression of a p120 catenin deletion mutant (p120622–628) or splice variant (p120-4A), neither of which could regulate Rho or Rac activity, showed no significant effect. The inhibition of GLUT4 translocation was also observed upon the simultaneous expression of a constitutively active Rac mutant (Rac1/Val¹²) in combination with a dominant-interfering Rho mutant (RhoA/Asn¹⁹). This was recapitulated by expression of the Rho ADP-ribosylation factor (C3ADP) in combination with constitutively active Rac1/Val¹². Moreover, siRNA-mediated knockdown of p120 catenin resulted in increased basal state accumulation of GLUT4 at the plasma membrane. Together, these data demonstrate that p120 catenin plays an important role in maintaining the basal tone of membrane protein trafficking in adipocytes through the dual regulation of Rho and Rac function and accounts for reports implicating Rho or Rac in the control of GLUT4 translocation.

Received for publication, April 3, 2006 , and in revised form, June 5, 2006.

^* This study was supported by research Grants DK55811 and DK33823 from the National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed. Tel.: 631-444-3083; Fax: 631-444-3022; E-mail: Pessin{at}pharm.stonybrook.edu.

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