Purpose: Our results showed that C17orf37 is predominantly a membrane bound protein. However, C17orf37 protein does not have membrane localization sequence. The purpose of this study is to understand the molecular signaling mechanism that regulates activation and translocation of C17orf37 to the cell membrane, and identify potential interactors of C17orf37 that mediate downstream signaling.
Methods: By using different prenylase enzyme inhibitors we show that C17orf37 is preferentially prenylated by geranylgerany transferase I (GGTase I) enzyme. By yeast-two hybrid, immuno precipitation and fluorescence life time imaging microscopy (FLIM) we show C17orf37 is a novel interactor of annexin A2 and this interaction is important for cancer cell migration and invasion.
Results: Overexpression of C17orf37 resulted in increased expression of MMP-9, uPA and VEGF through activation of Akt and NF-?B pathway, thus increasing migration and invasion of prostate cancer cells. Cellular localization studies using confocal and total internal reflection microscopy (TIRF) demonstrated predominant expression of C17orf37 protein in the membrane. Careful examination of C17orf37 protein sequence revealed a C-terminal prenylation motif ‘CVIL’. We hypothesized that C17orf37 acts as a membrane bound signaling molecule and facilitates migration and invasion of prostate cancer cells by NF-kB mediated downstream target genes. Using inhibitors of prenyl transferase enzymes we demonstrate that C17orf37 is preferentially geranylgeranyled by GGTase-1 enzyme and inhibition of the enzyme leads to reduced membrane localized C17orf37 protein in both breast and prostate tumor cells. By yeast two hybrid analysis we identified annexin A2 as a novel interactor of C17orf37 and by fluorescence life time imaging microscopy based FRET assay we found that these two molecules physically interact at the membrane region. Our studies show C17orf37-annexin A2 interaction is critical for tumor cell invasion and metastasis.
Conclusions: C17orf37 regulates the expression of proteolytic enzymes by activating NF-kB. At the membrane, C17orf37 either directly or through annexin A2 controls the Akt activity. In summary, membrane bound C17orf37 acts as a signaling molecule and regulates migration and invasion of prostate cancer cells.