Identification of a novel family of laminin N-terminal alternate splice isoforms: structural and functional characterization

J Biol Chem. 2009 Dec 18;284(51):35588-96. doi: 10.1074/jbc.M109.052811.


The laminins are a family of heterotrimeric basement membrane proteins that play roles in cellular adhesion, migration, and tissue morphogenesis. Through in silico analysis of the laminin-encoding genes, we identified a novel family of alternate splice isoforms derived from the 5'-end of the LAMA3 and LAMA5 genes. These isoforms resemble the netrins in that they contain a laminin N-terminal domain followed by a short stretch of laminin-type epidermal growth factor-like repeats. We suggest the terms LaNt (laminin N terminus) alpha3 and LaNt alpha5, for the predicted protein products of these mRNAs. RT-PCR confirmed the presence of these transcripts at the mRNA level. Moreover, they exhibit differential, tissue-specific, expression profiles. To confirm the existence of LaNt alpha3 protein, we generated an antibody to a unique domain within the putative polypeptide. This antibody recognizes a protein at the predicted molecular mass of 64 kDa by immunoblotting. Furthermore, immunofluorescence analyses revealed a basement membrane staining in epithelial tissue for LaNt alpha3 and LaNt alpha3 localized along the substratum-associated surface of cultured keratinocytes. We have also tested the functionality LaNt alpha3 through RNAi-mediated knockdown. Keratinocytes exhibiting specific knockdown of LaNt alpha3 displayed impaired adhesion, stress resistance, and reduced ability to close scratch wounds in vitro.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing / physiology*
  • Animals
  • Antibodies, Monoclonal / chemistry
  • Cell Adhesion / physiology
  • HeLa Cells
  • Humans
  • Keratinocytes / cytology
  • Keratinocytes / metabolism*
  • Laminin / biosynthesis*
  • Laminin / genetics
  • Mice
  • Organ Specificity / physiology
  • Protein Isoforms / biosynthesis
  • Protein Isoforms / genetics
  • Protein Structure, Tertiary / physiology
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Wound Healing / physiology


  • Antibodies, Monoclonal
  • Laminin
  • Protein Isoforms
  • RNA, Messenger
  • laminin alpha5
  • laminin alpha 3