Cystathionine γ-lyase overexpression inhibits cell proliferation via a H2S-dependent modulation of ERK1/2 phosphorylation and p21Cip/WAK-1

Cystathionine gamma-lyase (CSE) is a key enzyme in the trans-sulfuration pathway. CSE uses L-cysteine as a substrate to produce hydrogen sulfide (H2S). The CSE/H2S system has been shown to play an important role in regulating cellular functions in different systems. In the present study, we used CSE stably overexpressed HEK293 cells to explore the effect of the CSE/H2S system on cell growth and proliferation. The overexpression of CSE resulted in increases in CSE mRNA levels, CSE proteins, and intracellular H2S production rates, as well as the inhibition of cell proliferation and DNA synthesis. These effects were accompanied by a sustained ERK activation and up-regulation of the cyclin-dependent kinase inhibitor p21(Cip/WAK-1). Blocking the action of ERK with U0126 inhibited the induction of p21(Cip/WAK-1), suggesting that ERK activation functions upstream of p21(Cip/WAK-1) activation to initiate the CSE overexpression-induced cell growth inhibition. The antiproliferative effect of CSE is likely mediated by endogenously produced H2S because the H2S scavenger methemoglobin (10 muM) significantly decreased the H2S production rate and reversed the antiproliferative effect afforded by CSE. Exogenous H2S (100 muM) also inhibited cell proliferation. However, the other CSE-catalyzed products, ammonium and pyruvate, failed to inhibit cell proliferation. Methemoglobin also abolished the inhibitory effect of exogenous H2S on cell proliferation. Moreover, exogenous H2S induced a sustained ERK and p21(Cip/WAK-1) activation. These findings support the hypothesis that endogenously produced H2S may play a fundamental role in cell proliferation and survival.