Mutant K-ras regulates cathepsin B localization on the surface of human colorectal carcinoma cells

Neoplasia. Nov-Dec 2003;5(6):507-19. doi: 10.1016/s1476-5586(03)80035-0.


Cathepsin B protein and activity are known to localize to the basal plasma membrane of colon carcinoma cells following the appearance of K-ras mutations. Using immunofluorescence and subcellular fractionation techniques and two human colon carcinoma cell lines - one with a mutated K-ras allele (HCT 116) and a daughter line in which the mutated allele has been disrupted (HKh-2)-we demonstrate that the localization of cathepsin B to caveolae on the surface of these carcinoma cells is regulated by mutant K-ras. In HCT 116 cells, a greater percentage of cathepsin B was distributed to the caveolae, and the secretion of cathepsin B and pericellular (membrane-associated and secreted) cathepsin B activity were greater than observed in HKh-2 cells. Previous studies established the light chain of annexin II tetramer, p11, as a binding site for cathepsin B on the surface of tumor cells. The deletion of active K-ras in HKh-2 cells reduced the steady-state levels of p11 and caveolin-1 and the distribution of p11 to caveolae. Based upon these results, we speculate that cathepsin B, a protease implicated in tumor progression, plays a functional role in initiating proteolytic cascades in caveolae as downstream components of this cascade (e.g., urokinase plasminogen activator and urokinase plasminogen activator receptor) are also present in HCT 116 caveolae.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Annexin A2 / genetics
  • Annexin A2 / metabolism*
  • Cathepsin B / metabolism*
  • Caveolae / metabolism
  • Caveolin 1
  • Caveolins / genetics
  • Caveolins / metabolism
  • Cell Line, Tumor
  • Cell Membrane / metabolism*
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Fluorescent Antibody Technique
  • Genes, ras / genetics*
  • Humans
  • Immunoblotting
  • Immunohistochemistry
  • Microscopy, Confocal
  • Mutation
  • Protein Transport / physiology
  • Receptors, Cell Surface / metabolism
  • Receptors, Urokinase Plasminogen Activator
  • S100 Proteins / genetics
  • S100 Proteins / metabolism*
  • Urokinase-Type Plasminogen Activator / metabolism


  • Annexin A2
  • CAV1 protein, human
  • Caveolin 1
  • Caveolins
  • PLAUR protein, human
  • Receptors, Cell Surface
  • Receptors, Urokinase Plasminogen Activator
  • S100 Proteins
  • S100 calcium binding protein A10
  • Urokinase-Type Plasminogen Activator
  • Cathepsin B