Dataset Information

Molecular cloning of the rat integrin alpha 1-subunit: a receptor for laminin and collagen.

ABSTRACT: Integrin heterodimers mediate a variety of adhesive interactions, including neuronal attachment to and process outgrowth on laminin. We report here the cloning and primary sequence of an M-200 kD integrin alpha subunit that associates with the integrin beta 1 subunit to form a receptor for both laminin and collagen. Similarities in ligand-binding specificity, relative molecular mass and NH2-terminal sequence make this a strong candidate for the rat homologue of the alpha subunit of the human integrin VLA-1. The full-length rat alpha 1 cDNAs encode a protein containing a purative signal sequence and a mature polypeptide of 1,152 amino acids, with extracellular, transmembrane and cytoplasmic domains. Several structural features are conserved with other integrin alpha chains, including (a) a sequence motif repeated seven times in the NH2-terminal half; (b) potential Ca2+/Mg2+ binding sites in repeats 5, 6, and 7, and (c) alignment of at least 14 of 23 cysteine residues. This rat alpha 1 sequence also contains a 206-amino acid I domain, inserted between repeats 2 and 3, that is homologous to I domains found in the same position in the alpha subunits of several integrins (VLA-2, Mac-1, LFA-1, p150). The rat alpha 1 and human VLA-2 apha subunits share greater than 50% sequence identity in the seven repeats and I domain, suggesting that these sequence identities may underlie some of their similar ligand-binding specificities. However, the rat integrin alpha 1 subunit has several unique features, including a 38-residue insert between two Ca2+/Mg2+ binding domains, and a divergent 15-residue cytoplasmic sequence, that may potentially account for unique functions of this integrin.

SUBMITTER: Ignatius MJ

PROVIDER: S-EPMC2116196 | biostudies-other | 1990 Aug

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:We recently purified the rat liver hyaluronan receptor for endocytosis (HARE) and found abundant expression of 175- and approximately 300-kDa HARE species in sinusoidal endothelial cells of the liver, spleen, and lymph nodes. We report herein the first cloning and functional expression of the rat 175-kDa HARE. Peptide sequences were obtained from the purified 175-kDa HARE, and degenerate oligonucleotide primers were designed for reverse transcription-polymerase chain reaction and cDNA cloning. Results of 5'-rapid amplification of cDNA ends, Northern analysis, N-terminal sequence, and antibody reactivity analyses indicated the absence of mRNA directly encoding the 175-kDa HARE. This protein is most likely derived from a larger precursor. Accordingly, we constructed an artificial 4.7-kb cDNA encoding the 1431 amino acid 175-kDa HARE. The predicted type I membrane protein has a mass of 156,393 Da and a pI of 7.86. The 175-kDa HARE cDNA, fused to the N-terminal leader sequence of the Ig kappa-chain, was transfected transiently into COS-7 cells and stably into SK-Hep-1 cells, respectively, to assess hyaluronan or hyaluronic acid (HA)-binding activity and endocytosis. In both cases, HARE expression and HA-binding activity were detected. Furthermore, stable SK-175HARE cells demonstrated specific endocytosis of (125)I-HA and receptor recycling. Fluorescence-activated cell sorting analysis confirmed that recombinant HARE was expressed on the cell surface and that fluorescent HA uptake was inhibited by a specific blocking monoclonal antibody against HARE. Additionally, HARE was substantially colocalized with clathrin, but not with internalized HA that was delivered to lysosomes. The results confirm that recombinant 175-kDa HARE is an authentic endocytic receptor for HA and that this receptor can function independently of the approximately 300-kDa HARE. HARE is the first functionally identified member of a protein family that shares a similar organization of Fasciclin, epidermal growth factor-like, Xlink, and transmembrane domains.

Dataset Information

Molecular cloning of the rat integrin alpha 1-subunit: a receptor for laminin and collagen.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets