Isolation, Cloning, and Sequence Analysis of the Integrin Subunit α10, a β1-associated Collagen Binding Integrin Expressed on Chondrocytes*
- From the ‡Department of Cell and Molecular Biology, Section for Cell and Matrix Biology, Lund University, S-221 00 Lund and the ¶Ludwig Institute for Cancer Research, S-75124 Uppsala, Sweden
Abstract
We have found that chondrocytes express a novel collagen type II-binding integrin, a new member of the β1-integrin family. The integrin α subunit, which has aM r of 160 kDa reduced, was isolated from bovine chondrocytes by collagen type II affinity purification. The human homologue was obtained by screening a human chondrocyte library with a bovine cDNA probe. Cloning and cDNA sequence analysis of the human integrin α subunit designated α10 show that it shares the general structure of other integrin α subunits. The predicted amino acid sequence consists of a 1167-amino acid mature protein, including a signal peptide (22 amino acids), a long extracellular domain (1098 amino acids), a transmembrane domain (25 amino acids), and a short cytoplasmic domain (22 amino acids). The extracellular part contains a 7-fold repeated sequence, an I-domain (199 amino acids) and three putative divalent cation-binding sites. The deduced amino acid sequence of α10 is 35% identical to the integrin subunit α2 and 37% identical to the integrin subunit α1. Northern blot analysis shows a single mRNA of 5.4 kilobases in chondrocytes. A peptide antibody against the predicted sequence of the cytoplasmic domain of α10 immunoprecipitated two proteins with masses of 125 and 160 kDa from chondrocyte lysates under reducing conditions. The peptide antibody specifically stained chondrocytes in tissue sections of human articular cartilage, showing that α10β1 is expressed in cartilage tissue.
Footnotes
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↵* The work was supported by grants from the Swedish Medical Research Council, Anna-Greta Crafoord’s Stiftelse, Crafoord’s stiftelser, Gustav V’s 80-års fond, Greta och Johan Kock’s stiftele, Kungliga fysiografiska sällskapets stiftelse, Riksföreningen mot reumatism, Magnus Bergvall’s Stiftelse, Thelma Zoe′ga’s fond, and Alfred Österlund’s Stiftelse.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AF074015.
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↵§ Dept. of Cell and Molecular Biology, Section for Cell and Matrix Biology, Lund University, P.O. Box 94, S-221 00 Lund, Sweden. Tel.: +46-46-222-3126; Fax: 46-46-222-3128; E-mail: lisbet.camper{at}medkem.lu.se.
- Abbreviations:
- PBS
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phoshate-buffered saline
- PAGE
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polyacrylamide gel electrophoresis
- PCR
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polymerase chain reaction
- RACE (Race)
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rapid amplification of the cDNA end.
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- Received February 6, 1998.
- Revision received May 13, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
