Journal Article

G1-G2 Aggrecan Product that can be Generated by M-calpain on Truncation at Ala<sup>709</sup>–Ala<sup>710</sup> is Present Abundantly in Human Articular Cartilage

Hideaki Maehara, Kiichi Suzuki, Tomohiro Sasaki, Hidefumi Oshita, Eriko Wada, Toshiyuki Inoue and Katsuji Shimizu

in The Journal of Biochemistry

Published on behalf of The Japanese Biochemical Society

Volume 141, issue 4, pages 469-477
Published in print April 2007 | ISSN: 0021-924X
Published online January 2007 | e-ISSN: 1756-2651 | DOI: https://dx.doi.org/10.1093/jb/mvm052
G1-G2 Aggrecan Product that can be Generated by M-calpain on Truncation at Ala709–Ala710 is Present Abundantly in Human Articular Cartilage

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To elucidate the specific function of m-calpain in the metabolism of aggrecan in human articular cartilage, the prevalence and localization of a large glycosaminoglycan-bearing aggrecan product generated by m-calpain in human osteoarthritis (OA) cartilage were investigated. Extracts of human OA articular cartilage were analysed by immunostaining using new polyclonal anti-VPGVA antiserum that detects the COOH terminal neoepitope IVTQVVPGVA709 generated by m-calpain-related cleavage within the keratan sulphate rich region of human aggrecan. Immunoblotting analyses of aggrecan populations in guanidine hydrochloride-extracts showed that OA cartilages contained anti-VPGVA positive aggrecan products with the COOH terminal neoepitope … VPGVA709, resulting from truncation between the Ala709–Ala710 m-calpain-related cleavage site. This aggrecan product consisted of two NH2 terminal globular domain (G1 and G2) and KS side chains. Immunohistochemical staining showed that anti-VPGVA positive staining was localized within chondrocytes and spread to the surrounding interterritorial matrix. Confocal microscopic analysis showed subcellular colocalization of anti-VPGVA and anti m-calpain. These results indicate that the aggrecan product with the COOH terminal neoepitope VPGVA709 is synthesized regularly by intracellular processing in chondrocytes, and is present abundantly as a limited form of aggrecan. M-calpain is the major candidate of the proteinase to generate this aggrecan product during the intracellular aggrecan processing.

Keywords: aggrecan; human osteoarthritis; keratan sulphate; m-calpain; proteoglycan

Journal Article.  4933 words.  Illustrated.

Subjects: Biochemistry

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