Title :
Adiponectin multimerization is dependent on conserved
lysines in the collagenous
domain : evidence for regulation of multimerization by alterations in posttranslational modifications
Abstract :
- Adiponectin is a secreted, multimeric protein with insulin-sensitizing, antiatherogenic, and antiinflammatory properties
- Serum adiponectin consists of trimer, hexamer, and larger high-molecular-weight (HMW) multimers, and these HMW multimers appear to be the more bioactive forms
- Multimer com position of adiponectin appears to be regulated; however, the molecular mechanisms involved are unknown
- We hypothesize that regulation of adiponectin multimerization and secretion occurs via changes in posttranslational modifications ( PTMs )
- Although a structural role for intertrimer disulfide bonds in the formation of hexamers and HMW multimers is established, the role of other PTMs is unknown
- PTMs identified in murine and bovine adiponectin include hydroxylation of multiple conserved proline and lysine residues and glycosylation of hydroxylysines
- By mass spectrometry, we confirmed the presence of these PTMs in human adiponectin and identified three additional hydroxylations on Pro71, Pro76, and Pro95
- We also investigated the role of the five modified lysines in multimer formation and secretion of recombinant human adiponectin expressed in mammalian cell lines
- Mutation of modified lysines in the collagenous domain prevented formation of HMW multimers, whereas a pharmacological inhibitor of prolyl- and lysyl-hydroxylases, 2,2'-dipyridyl, inhibited formation of hexamers and HMW multimers
- Bacterially expressed human adiponectin displayed a complete lack of differentially modified isoforms and failed to form bona fide trimers and larger multimers
- Finally, glucose-induced increases in HMW multimer production from human adipose explants correlated with changes in the two-dimensional electrophoresis profile of adiponectin isoforms
- Collectively, these data suggest that adiponectin multimer com position is affected by changes in PTM in response to physiological factors