Intracellular pH modulates vimentin remodeling in response to oxidants

Abstract

AbstractThe intermediate filament protein vimentin plays key roles in the integration of cytoskeletal functions with impact on essential cellular processes including migration, mitosis and autophagy. Moreover, vimentin is involved in pathological processes such as cancer, fibrosis and interaction with pathogens. The vimentin network is finely tuned by posttranslational modifications, among which, those affecting its single cysteine residue (C328) play a critical role not only in vimentin function, but also in its interplay with actin. Interestingly, C328 exhibits a low pKa, which favors the presence of the thiol group in the thiolate form, and therefore its reactivity, at physiological pH. Therefore, C328 reactivity and modifications could be modulated by pH fluctuations in the physiological range. Here we show that indeed, vimentin cysteine oxidation and alkylation, and the subsequent vimentin remodeling, can be modulated as a function of pH, in vitro and in cells. Lowering intracellular pH by several means renders vimentin unresponsive to disruption by oxidants, whereas provoking an intracellular alkalinization exerts a sensitizing effect. The protective effect of low pH appears selective for vimentin since it does not preclude oxidant-elicited disruption of actin or tubulin structures. Importantly, a C328A vimentin mutant is resistant to disruption by oxidants under all pH conditions, highlighting the role of the thiol group at this position in the pH-dependent modulation of vimentin susceptibility to oxidants. Taken together, these results put forward intracellular pH as a key factor modulating redox-dependent vimentin remodeling.