Mutant K-ras Regulates Cathepsin B Localization on the Surface of Human Colorectal Carcinoma Cells

• Published in: Neoplasia (New York, N.Y.) N.Y.), 2003-11, Vol.5 (6), p.507-519
• Main Authors: Cavallo-Medved, Dora, Dosescu, Julie, Linebaugh, Bruce E., Sameni, Mansoureh, Rudy, Debbie, Sloane, Bonnie F.
• Format: Article
• Language: English
• Subjects: Annexin A2 - genetics; Annexin A2 - metabolism; Cancer; Cathepsin B - metabolism; caveolae; Caveolae - metabolism; Caveolin 1; Caveolins - genetics; Caveolins - metabolism; Cell Line, Tumor; Cell Membrane - metabolism; Colorectal Neoplasms - genetics; Colorectal Neoplasms - metabolism; cysteine professes; Electrophoresis, Polyacrylamide Gel; Fluorescent Antibody Technique; Genes, ras - genetics; Humans; Immunoblotting; Immunohistochemistry; K-ras; membrane-associated professes; 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
• ISSN: 1476-5586; 1522-8002; 1476-5586; 1522-8002
• 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 pl1 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.