Chondrocyte-matrix interactions: with emphasis on the collagen binding integrin a10ß1

Sammanfattning: The work in this thesis has been focused on chondrocyte integrins and their interaction with the matrix proteins chondroadherin (CHAD) and collagen type II (CII). Affinity purification of CHAD-binding proteins from chondrocyte lysate, followed by immunoprecipitation of EDTA-eluted material identified alpha2beta1 as a CHAD-binding integrin. Interaction between alpha2beta1 and CHAD was found to prevent cell-spreading which was in contrast to the interaction between alpha2beta1 and CII.The thesis also describe the purification, cloning and sequence analysis of the novel collagen-binding integrin subunit alpha10 which is a member of the beta1-integrin family. An antibody against the cytoplasmic domain of alpha10 demonstrated that alpha10beta1 is expressed by chondrocytes in cartilage tissues and also by cells in the ossification groove of Ranvier, muscle epimysium, tendon/ligament sheaths and in aortic and atrioventricular valves of the heart. It is also demonstrated that alpha10 exist as two splice variants. Both splice forms are present in alpha10 expressing tissues, although the shorter form predominated in cells from articular cartilage and aortic valve as judged by PCR experiments. The longer form was upregulated when chondrocytes dedifferentiated in monolayer culture. The exon/intron boundaries of the mouse alpha10 gene was characterized and the gene was mapped to mouse chromosome 3F2.2 and human chromosome 1q21.