title: Identification and recombinant production of human laminin alpha4 subunit splice variants.
abstract: Laminins, the major basement membrane glycoproteins, are composed of three subunits. We identified a splice variant of the human laminin alpha4 subunit transcript containing 21 extra nucleotides. A heptapeptide sequence, MDCPTIS, was inserted close to the two cysteine residues possibly involved in the intersubunit disulfide bonds. Both the authentic alpha4 subunit (alpha4A) and the variant with the heptapeptide insertion (alpha4B) were readily secreted as laminin-8 trimers (alpha4Abeta1gamma1 or alpha4Bbeta1gamma1) upon cotransfection with expression vectors for the beta1 and gamma1 subunits. The purified recombinant laminin-8 containing the alpha4B subunit was more potent in promoting cell spreading than that containing alpha4A, raising the possibility that the alternative splicing of the alpha4 subunit transcript regulates the cell-adhesive activity of laminin-8. Since both alpha4A and alpha4B transcripts were detected by RT-PCR in several human cell lines, these two isoforms of laminin-8 with differing cell-adhesive activities are present in the basement membranes of human tissues.
authors.affiliation: Sekiguchi Biomatrix Signaling Project, Exploratory Research for Advanced Technology Organization, Japan Science and Technology Corporation, 21 Karimata, Yazako, Nagakute-cho, Aichi, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Kil Hwan
authors.initials: KH
authors.lastname: Kim
authors.forename: Hironobu
authors.initials: H
authors.lastname: Fujiwara
authors.forename: Chisei
authors.initials: C
authors.lastname: Shimono
authors.forename: Megumi
authors.initials: M
authors.lastname: Yamashita
authors.forename: Noriko
authors.initials: N
authors.lastname: Sanzen
authors.forename: Sugiko
authors.initials: S
authors.lastname: Futaki
authors.forename: Kiyotoshi
authors.initials: K
authors.lastname: Sekiguchi
mesh_terms: D017398:Alternative Splicing; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D003001:Cloning, Molecular; D006801:Humans; D007797:Laminin / Q000235:genetics* / Q000378:metabolism; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
chemical_list: C501369:LAMA4 protein, human; D007797:Laminin; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; C110308:laminin 8