The tumour-associated antigen L6 (L6-Ag) is recruited to the tetraspanin-enriched microdomains: implication for tumour cell motility

J Cell Sci. 2008 Mar 1;121(Pt 5):685-94. doi: 10.1242/jcs.020347. Epub 2008 Feb 12.

Abstract

Tumour-associated antigen L6 (L6-Ag, also known as TM4SF1) regulates tumour cell motility and invasiveness. We found that L6-Ag is abundant on the plasma membrane and on intracellular vesicles, on which it is co-localised with the markers for late endosomal/lysosomal compartments, including Lamp1/Lamp2 proteins and LBPA. Antibody internalisation and live-imaging experiments suggested that L6-Ag is targeted to late endocytic organelles (LEO) predominantly via a biosynthetic pathway. Mapping experiments showed that the presence of transmembrane regions is sufficient for directing L6-Ag to LEO. On the plasma membrane, L6-Ag is associated with tetraspanin-enriched microdomains (TERM). All three predicted cytoplasmic regions of L6-Ag are crucial for the effective recruitment of the protein to TERM. Recruitment to TERM correlated with the pro-migratory activity of L6-Ag. Depletion of L6-Ag with siRNA has a selective effect on the surface expression of tetraspanins CD63 and CD82. By contrast, the expression levels of other tetraspanins and beta1 integrins was not affected. We found that L6-Ag is ubiquitylated and that ubiquitylation is essential for its function in cell migration. These data suggest that L6-Ag influences cell motility via TERM by regulating the surface presentation and endocytosis of some of their components.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, CD / metabolism
  • Antigens, Surface / genetics
  • Antigens, Surface / metabolism*
  • COS Cells
  • Cell Adhesion / physiology
  • Cell Movement / physiology*
  • Chlorocebus aethiops
  • Down-Regulation / genetics
  • Endocytosis / physiology
  • HeLa Cells
  • Humans
  • Kangai-1 Protein / metabolism
  • Lysosomes / metabolism
  • Membrane Microdomains / metabolism*
  • Membrane Microdomains / ultrastructure
  • Membrane Proteins / metabolism*
  • Neoplasm Invasiveness / physiopathology*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Neoplasms / metabolism*
  • Platelet Membrane Glycoproteins / metabolism
  • Protein Transport / physiology
  • RNA, Small Interfering / metabolism
  • Tetraspanin 30
  • Transport Vesicles / metabolism
  • Ubiquitination / physiology

Substances

  • Antigens, CD
  • Antigens, Surface
  • CD63 protein, human
  • CD82 protein, human
  • Kangai-1 Protein
  • Membrane Proteins
  • Neoplasm Proteins
  • Platelet Membrane Glycoproteins
  • RNA, Small Interfering
  • Tetraspanin 30
  • TM4SF1 protein, human