Sequence and Tissue Distribution of the Integrin α9 Subunit, a Novel Partner of β1 That Is Widely Distributed in Epithelia and Muscle

• Published in: The Journal of cell biology 1993-12, Vol.123 (5), p.1289-1297
• Main Authors: Palmer, Elise L., Rüegg, Curzio, Ferrando, Ronald, Pytela, Robert, Sheppard, Dean
• Format: Article
• Language: English
• Subjects: Amino acids; Antiserum; Biological and medical sciences; Cell adhesion; Cell interactions, adhesion; Cell lines; Complementary DNA; Endothelial cells; Epithelial cells; Fundamental and applied biological sciences. Psychology; Hepatocytes; Integrins; Molecular and cellular biology; Polymerase chain reaction
• ISSN: 0021-9525; 1540-8140

The integrin family of adhesion receptors consists of several heterodimeric glycoproteins, each composed of one α and one β subunit. A novel integrin α subunit partial cDNA isolated from TGF-β stimulated guinea pig airway epithelial cells has previously been reported. We have now determined cDNA and amino acid sequence for the human homolog of this subunit, named α9, from a human lung cDNA library, a human small intestine cDNA library, and cDNA from the cell lines U937, HL-60 and Tera-2. This sequence is predicted to encode a 1006-amino acid mature protein that shares 39% identity with the previously identified integrin subunit α4. By Northern blot analysis, α9 mRNA was detected in the human carcinoma cell lines Tera-2 and Caco-2. Anti-peptide antibodies against the predicted COOH-terminal sequence of α9 immunoprecipitated a heterodimer (140 kD/115 kD nonreduced; 150 kD/130 kD reduced) from Tera-2 lysates. Immunodepletion of β1-containing integrins with Tera-2 lysates removed α9 immunoreactivity, suggesting that β1 is the principal β subunit partner for α9 in these cells. α9 was detected by immunohistochemistry in airway epithelium, in the basal layer of squamous epithelium, and in smooth muscle, skeletal muscle, and hepatocytes.