PAR-1- and PAR-3-type thrombin receptor expression in primary cultures of human renal cell carcinoma cells.

In this study, we report coexpression of proteinase-activated receptor (PAR)-1- and PAR-3-type thrombin receptors in primary cultures obtained from surgically resected specimens of renal cell carcinomas (RCCs). Receptor expression on RNA level was evaluated by using the RT-PCR technique. Results demonstrated the presence of mRNA encoding PAR-1 and PAR-3, but mRNA encoding PAR-4 could not be found in human RCC cells. The expression of PAR-1 and PAR-3 on protein level was investigated with confocal laser fluorescence and freeze-fracture electron microscopy. Both thrombin receptor types were localized on the cell membrane but were also found on intracellular compartments of RCC cells. On the outer cell membrane, clustering of PAR-1 and PAR-3 molecules was partly observed. This is the first study demonstrating presence of both PAR-1 and PAR-3 in human carcinoma cells.