Molecular cloning of the alpha subunit of human and guinea pig leukocyte adhesion glycoprotein Mo1: chromosomal localization and homology to the alpha subunits of integrins.

M. A. Arnaout, E. Remold-O'Donnell, M. W. Pierce, P. Harris, D. G. Tenen

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The cell-surface glycoprotein Mo1 is a member of the family of leukocyte cell adhesion molecules (Leu-CAMs) that includes lymphocyte function-associated antigen 1 (LFA-1) and p150,95. Each Leu-CAM is a heterodimer with a distinct alpha subunit noncovalently associated with a common beta subunit. Leu-CAMs play crucial roles in cell-cell and cell-matrix interactions. We describe the isolation and analysis of two partial cDNA clones encoding the alpha subunit of the Leu-CAM Mo1 in humans and guinea pigs. A monoclonal antibody directed against an epitope in the carboxyl-terminal portion of the guinea pig alpha chain was used for immunoscreening a lambda gt11 expression library. The sequence of a 378-base-pair insert from one immunoreactive clone revealed a single continuous open reading frame encoding 126 amino acids including a 26-amino acid tryptic peptide isolated from the purified guinea pig alpha subunit. A cDNA clone of identical size was isolated from a human monocyte/lymphocyte cDNA library by using the guinea pig clone as a probe. The human clone also encoded a 126-amino acid peptide including the sequence of an additional tryptic peptide present in purified human Mo1 alpha chain. RNA gel blots revealed that mature Mo1 alpha chain mRNA is approximately 5 kilobases in guinea pigs and humans. Southern analysis of DNA from hamster-human hybrids localized the human Mo1 alpha chain to chromosome 16, which has been shown to contain the gene for the alpha chain of lymphocyte function-associated antigen 1. A comparison of the Mo1 alpha chain coding region revealed significant homologies with carboxyl-terminal portions of the alpha subunits of fibronectin, vitronectin, and platelet IIb/IIIa receptors. These data suggest that the alpha subunits of Leu-CAMs evolved by gene duplication from a common ancestral gene and strengthen the hypothesis that the alpha subunits of these heterodimeric cell adhesion molecules on myeloid and lymphoid cells, platelets, and fibroblasts are evolutionary related.

Original languageEnglish (US)
Pages (from-to)2776-2780
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - Apr 1988


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