Intracellular interaction of FNDC1/FN1/AR/cMYC in prostate cancer cells

MicroRNAs play an important role in modulating normal cellular functions through protein-protein interaction in addition to regulating gene expression via mRNA degradation or translational repression. PVT1 is a non-protein coding gene that encodes six annotated microRNAs (miRNAs), including miR-1207-3p, a demonstrated modulator in PCa. MiR-1207-3p is significantly underexpressed in PCa cells when compared to normal prostatic cells and directly targets fibronectin type III domain containing 1 (FNDC1), which was found to be overexpressed in PCa cells along with concomitant overexpression of fibronectin (FN1)/androgen receptor (AR)/c-MYC. To better understand the role of FNDC1/FN1/AR/c-MYC in PCa progression we examined the interaction between FNDC1/FN1/AR/c-MYC. Coimmunoprecipitation study showed direct physical interaction between FNDC1/FN1/AR/c-MYC in PCa cells and FN1/AR/cMYC in normal prostatic cell. Knockdown of FN1, AR and cMYC not only confirmed FN1/FNDC1/AR/cMYC interaction but also gave rise to the possibility of a complex. We also examined the spatial localization of the FNDC1/FN1/AR/c-MYC pathway by performing immunofluorescence staining in PCa cells. Single staining analysis revealed that FNDC1, AR and c-MYC localize to the nucleus and cytoplasm while FN1 localizes only to the cytoplasm in PCa cells but not in the non-tumorigenic prostate cells. However, our findings show that miR-1207-3p has no direct effect on the FNDC1/FN1/AR/cMYC interaction. Understanding this molecular interaction can reveal additional insights into the role of FNDC1/FN1/AR/cMYC interaction in PCa progression.