Stress-induced RNASET2 overexpression mediates melanocyte apoptosis via the TRAF2 pathway in vitro

Abstract

The recent genome-wide association study identified a link between vitiligo and genetic variants in the ribonuclease T2 (RNASET2) gene; however, the functional roles of RNASET2 in vitiligo pathogenesis or in melanocyte apoptosis have yet to be determined. The current study was designed to investigate the vitiligo-related expression pattern of RNASET2 and its molecular function involving apoptosis-related signaling proteins and pathways. The results showed overexpression of RNASET2 in epidermis specimens from 40 vitiligo patients compared with that from matched healthy controls. In addition, in vitro analyses indicated that overexpression of RNASET2 was inducible in cultured primary human melanocytes and keratinocytes by stress conditions, that is, exposure to UV irradiation, hydrogen peroxide, and inflammatory factors, respectively, and led to increased cell apoptosis via the tumor necrosis factor receptor-associated factor 2 (TRAF2)–caspases pathway through the physical interaction of RNASET2 with TRAF2. Thus, RNASET2 may contribute to vitiligo pathogenesis by inhibiting TRAF2 expression and, as such, RNASET2 may represent a potential therapeutic target of vitiligo.

RNASET2 is required for ROS propagation during oxidative stress-mediated cell death

“…34 Drosophila expresses one RNASET2 homolog, RNase X25, which is induced by ROS and promotes cell death when overexpressed. 28,35 Constitutive, whole body knockdown of RNase X25 did not result in viable progeny, underscoring the importance of RNase X25 in general housekeeping functions. However, flies with fat body-specific knockdown of RNase X25 were viable and had similar body weight to WT flies (Figure 7a).…”

“…Several reports have described biological roles for T2 family members that are independent of catalytic activity. [26][27][28] To determine whether catalytic activity is required for the role of RNASET2 in lipotoxicity, we carried out complementation studies. A catalytically inactive (CI) murine RNASET2 construct was generated through site-directed mutagenesis of two of the three catalytic histidines.…”

“…27 In mammalian cells, expression of RNASET2 family members is induced in response to exposure to hydrogen peroxide, ultraviolet irradiation, and inflammatory stimuli. 28,35 Moreover, overexpression of this enzyme in melanocytes and keratinocytes sensitizes cells to oxidative-stress-induced apoptosis. 28 Our study extends these findings in several important ways.…”

“…28,35 Moreover, overexpression of this enzyme in melanocytes and keratinocytes sensitizes cells to oxidative-stress-induced apoptosis. 28 Our study extends these findings in several important ways. First, we demonstrate that loss-of-function of RNASET2 protects mammalian fibroblasts from nutrient excess and generalized oxidative stress, providing the first demonstration that RNASET2 is an essential protein in mammalian cell death responses.…”

“…The requirement for enzymatic activity of RNASET2 in lipotoxic cell death contrasts with studies showing that CI RNASET2 inhibits tumorigenesis of ovarian tumor cell lines and amplifies apoptotic cell death in response to hydrogen peroxide when overexpressed in melanocytes and keratinocytes. 28,39 Emerging evidence that other RNases regulate gene expression post-transcriptionally through targeted mRNA degradation suggests the possibility that RNASET2 substrates could include mRNAs involved in antioxidant responses. [40][41][42] Identification of the relevant RNASET2 substrates in future studies will provide important insights into its impact on cellular oxidative stress responses.…”