The major CD9 and CD81 molecular partner. Identification and characterization of the complexes

J Biol Chem. 2001 Apr 27;276(17):14329-37. doi: 10.1074/jbc.M011297200. Epub 2001 Jan 18.


By associating with specific partner molecules and with each other, the tetraspanins are thought to assemble multimolecular complexes that may be especially relevant with respect to metastasis. We have previously identified a 135-kDa molecule (CD9P-1) as a major molecular partner of CD9 in cancer cell lines. This molecule was identified, after immunoaffinity purification and mass spectrometry analysis, as the protein encoded by the KIAA1436 gene and the human ortholog of a rat protein known as FPRP. Cross-linking experiments detected a complex of the size of CD9 plus CD9P-1, showing that these glycoproteins directly associate with each other, probably in the absence of any other molecule. The use of chimeric CD9/CD82 molecules revealed the role of the second half of CD9, comprising the large extracellular loop and the fourth transmembrane domain. CD9P-1 was also shown to form separate complexes with CD81 and with an unidentified 175-kDa molecule. It also associated with other tetraspanins under conditions maintaining tetraspanin/tetraspanin interactions. The identification of a protein strongly linked to the tetraspanin web and the production of a specific monoclonal antibody will help to further characterize the role of this "web" under physiological and pathological conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal / metabolism
  • Antigens, CD / chemistry*
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism*
  • Cross-Linking Reagents / pharmacology
  • DNA, Complementary / metabolism
  • Flow Cytometry
  • Fluorescent Antibody Technique, Indirect
  • Glycoside Hydrolases / metabolism
  • HeLa Cells
  • Humans
  • Mass Spectrometry
  • Membrane Glycoproteins*
  • Membrane Proteins / chemistry
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Fluorescence
  • Neoplasm Proteins / chemistry*
  • Neoplasm Proteins / metabolism*
  • Neoplasm Transplantation
  • Plasmids / metabolism
  • Precipitin Tests
  • Protein Binding
  • Protein Structure, Tertiary
  • Rats
  • Tetraspanin 28
  • Tetraspanin 29
  • Transfection
  • Tumor Cells, Cultured


  • Antibodies, Monoclonal
  • Antigens, CD
  • CD81 protein, human
  • CD9 protein, human
  • Carrier Proteins
  • Cd81 protein, mouse
  • Cd81 protein, rat
  • Cd9 protein, mouse
  • Cross-Linking Reagents
  • DNA, Complementary
  • Membrane Glycoproteins
  • Membrane Proteins
  • Neoplasm Proteins
  • PTGFRN protein, human
  • Ptgfrn protein, rat
  • Tetraspanin 28
  • Tetraspanin 29
  • Glycoside Hydrolases