Differential G protein subunit expression by prostate cancer cells and their interaction with CXCR5

作者：El Haibi Christelle P; Sharma Praveen; Singh Rajesh; Gupta Pranav; Taub Dennis D; Singh Shailesh; Lillard James W Jr^*

来源：Molecular Cancer, 2013, 12(1): 64.

DOI：10.1186/1476-4598-12-64

• Prostate cancer
• Chemokine
• G proteins
• G protein-coupled receptor

with PCa progression, and mediate PCa cell migration and invasion following interaction with CXCL13. However, the differential expression of G protein alpha,beta, and. subunits by PCa cell lines and the precise combination of these proteins with CXCR5 has not been elucidated.
Methods: We examined differences in G protein expression of normal prostate (RWPE-1) and PCa cell lines (LNCaP, C4-2B, and PC3) by western blot analysis. Further, we immunoprecipitated CXCR5 with different G protein subunits, and CXCR4, following CXCL13 stimulation. To investigate constitutive coupling of CXCR5 with CXCR4 and PAR-1 we performed invasion assay in PCa cells transfected with G(aq/i2) or G(a13) siRNA, following CXCL13 treatment. We also investigated Rac and RhoA activity by G-LISA activation assay in PCa cells following CXCL13/thrombin stimulation.
Result: Of the 22 G proteins studied, G(ai1-3), G(beta 1-4), G(Y5), G(Y7), and G.10 were expressed by both normal and PCa cell lines. Gas was moderately expressed in C4-2B and PC3 cell lines, G(aq/11) was only present in RWPE-1 and LNCaP cell lines, while G(a12) and Ga-13 were expressed in C4-2B and PC3 cell lines. G.9 was expressed only in PCa cell lines. G(a16), G(beta 5), G(Y1-4), and G(Y13) were not detected in any of the cell lines studied. Surprisingly, CXCR4 co-immunoprecipitated with CXCR5 in PCa cell lines irrespective of CXCL13 treatment. We also identified specific G protein isoforms coupled to CXCR5 in its resting and active states. G(aq/11/)G(beta 3)/G(Y9) in LNCaP and G(ai2)/G(beta 3)/G(Y9) in C4-2B and PC3 cell lines, were coupled to CXCR5 and disassociated following CXCL13 stimulation. Interestingly, G(a13) co-immunoprecipitated with CXCR5 in CXCL13-treated, but not in untreated PCa cell lines. Inhibition of G(aq/i2) significantly decreased the ability of cells to invade, whereas silencing Ga13 did not affect CXCL13-dependent cell invasion. Finally, CXCL13 treatment significantly increased Rac activity in G(aq/i2) dependent manner, but not RhoA activity, in PCa cell lines.
Conclusions: These findings offer insight into molecular mechanisms of PCa progression and can help to design some therapeutic strategies involving CXCR5 and/or CXCL13 blockade and specific G protein inhibition to abrogate PCa metastasis.

• 出版日期2013-6-18