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A highly conserved tryptophan in the N-terminal variable domain regulates disulfide bond formation and oligomeric assembly of adiponectin

Authors


Alok K. Mitra, School of Biological Sciences, University of Auckland, Auckland 1030, New Zealand
Fax: +64 9 3737414
Tel: +64 9 9238162
E-mail: a.mitra@auckland.ac.nz
Yu Wang, Department of Pharmacology and Pharmacy, University of Hong Kong, Hong Kong, SAR, China
Fax: 00852 2818 5653
Tel: 00852 2819 2864
E-mail: yuwanghk@hkucc.hku.hk

Abstract

Adiponectin is a collagenous adipokine with direct anti-diabetic and anti-atherogenic properties. It can assume an ensemble of oligomeric states, e.g. trimers, hexamers and octadecamers, each being involved in distinct signaling pathways relevant to adiponectin’s diverse biological function in metabolism, immunity, inflammation and cellular homeostasis. Assembly of the active variants principally the octadecameric high molecular weight form is achieved via the tightly controlled oxidation of cysteine 39 located in the adiponectin hyper-variable domain (AHD, residues 18–44) between the signal sequence and the collagen-like domain. We show that mutation of a highly conserved tryptophan (W42A) in the AHD profoundly affects assembly by trapping full-length adiponectin in the oxidized trimeric or hexameric states with a concomitant major reduction in the high molecular weight form. Our biophysical measurements on synthesized analogues of the AHD suggests that the aberrant oligomer distribution can be explained based on the fact that the proximity of W42 to C39 causes a reduction in the rate of C39 oxidation, an effect that to our knowledge has not been documented before. At the biological level, the perturbed oligomer distribution of full-length mutant adiponectin leads to a major reduction in the AMP-activated protein kinase activation in endothelial cells and liver tissues.

Structured digital abstract

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