Testes-specific protease 50 (TSP50) promotes cell proliferation through the activation of the nuclear factor κB (NF-κB) signalling pathway

Abstract

TSP50 (testes-specific protease 50) is a testis-specific expression protein, which is expressed abnormally at high levels in breast cancer tissues. This makes it an attractive molecular marker and a potential target for diagnosis and therapy; however, the biological function of TSP50 is still unclear. In the present study, we show that overexpression of TSP50 in CHO (Chinese-hamster ovary) cells markedly increased cell proliferation and colony formation. Mechanistic studies have revealed that TSP50 can enhance the level of TNFα (tumour necrosis factor α)- and PMA-induced NF-κB (nuclear factor κB)-responsive reporter activity, IκB (inhibitor of NF-κB) α degradation and p65 nuclear translocation. In addition, the knockdown of endogenous TSP50 in MDA-MB-231 cells greatly inhibited NF-κB activity. Co-immunoprecipitation studies demonstrated an interaction of TSP50 with the NF-κB-IκBα complex, but not with the IKK (IκB kinase) α/β-IKKγ complex, which suggested that TSP50, as a novel type of protease, promoted the degradation of IκBα proteins by binding to the NF-κB-IκBα complex. Our results also revealed that TSP50 can enhance the expression of NF-κB target genes involved in cell proliferation. Furthermore, overexpression of a dominant-negative IκB mutant that is resistant to proteasome-mediated degradation significantly reversed TSP50-induced cell proliferation, colony formation and tumour formation in nude mice. Taken together, the results of the present study suggest that TSP50 promotes cell proliferation, at least partially, through activation of the NF-κB signalling pathway.

The Threonine Protease Activity of Testes-Specific Protease 50 (TSP50) Is Essential for Its Function in Cell Proliferation

“…Besides protease activity, TSP50 has also been shown to facilitate cell proliferation [5], [6]. To determine whether protease activity is essential to TSP50-mediated promotion of cell growth, we established a point mutant construct of TSP50, TSP50 T310A, a protease-dead mutant [11].…”

“…This could be one of the mechanisms underlying TSP50-mediated promotion of cell proliferation [6]. To determine how the TSP50 T310A mutation abolishes the effects of TSP50 on cell proliferation, the ability of the mutant TSP50s to interact with NF-κB:IκBα complex and to promote NF-κB signaling were examined.…”

“…TSP50, a newly discovered threonine protease, contains amino acid sequences and enzymatic structures similar to those of many serine proteases. It has been shown that overexpression of TSP50 can promote cell proliferation and colony formation in vitro and stimulate tumor formation in nude mice [6]. It has also been shown that knockdown of TSP50 in mouse P19 cells can inhibit tumor cell proliferation and induce apoptosis [5].…”

“…Downregulation of TSP50 expression has been found to reduce cell proliferation and colony formation [5]. Our previous studies have revealed that the overexpression of TSP50 in CHO cells can markedly promote cell proliferation and colony formation in vitro and stimulate tumor formation in nude mice [6]. These results indicate that TSP50 could be an oncogene.…”

Down-regulation of testes-specific protease 50 induces apoptosis in human laryngocarcinoma HEp2 cells in a NF-κB-mediated pathway

“…It also could promote the degradation of IjBa proteins through interacting with the NF-jB-IjBa complex [11][12][13]. Therefore, our research focused primarily on the relationship between TSP50 and NF-jB activation.…”