KISS1 is a broadly functional metastatic suppressor that is secreted and processed in the extracellular milieu into small peptides (called kisspeptins (KP)). The enzyme(s) responsible for generation of KP from nascent KISS1 is unknown, although sequence analysis (cleavage at KR or RR dibasic sites) suggests that members of the proprotein convertase family may be involved. We, therefore, hypothesized that enzyme(s) belonging to the proprotein convertase family process KISS1 to generate kisspeptins. To this end, we treated multiple melanomas and breast carcinoma cells overexpressing KISS1 with the proprotein convertase inhibitor Dec-RVKR-CMK and found that KISS1 processing was completely inhibited, strongly consistent with a role for proprotein convertases. To identify specific proprotein convertases responsible for KISS1 processing, we systematically analyzed the mRNA expression of the nine members of this family across numerous cell lines. We found a consistent expression of the three proteases - furin, PC5 and PC7 -suggesting one or combination of these three enzymes to be involved in KISS1 processing. shRNA-mediated knockdown of furin, PC5 and PC7 (individually and in combination) resulted in complete loss of KISS1 processing only in furin knockdown cells; whereas, no effect on processing was observed in PC5 or PC7 knockdown cells. Thus, when combined with previous studies showing post-secretion processing, extracellular furin was identified as the essential enzyme responsible for KISS1 proteolytic cleavage into kisspeptins. [Support: CA134981, Komen SAC110037, National Foundation for Cancer Research, Steiner Family Fellowship in Metastasis Research]

Citation Format: Sitaram Harihar, Keke M. Pounds, Tomoo Iwakuma, N G. Seidah, Danny R. Welch. Furin is required for processing KISS1 to kisspeptins. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3860. doi:10.1158/1538-7445.AM2013-3860