Regulation of Photosensitivity by the Hippo Pathway in Lupus Skin

by Selleckchem | Jan 25 2024

Objective: Photosensitivity is one of the most common manifestations of systemic lupus erythematosus (SLE), yet its pathogenesis is not well understood. The normal-appearing epidermis of patients with SLE exhibits increased ultraviolet B (UVB)-driven cell death that persists in cell culture. Here, we investigated the role of epigenetic modification and Hippo signaling in enhanced UVB-induced apoptosis seen in SLE keratinocytes.

Methods: We analyzed DNA methylation in cultured keratinocytes from SLE patients compared to keratinocytes from healthy controls (n = 6/group). Protein expression was validated in cultured keratinocytes using immunoblotting and immunofluorescence. An immortalized keratinocyte line overexpressing WWC1 was generated via lentiviral vector. WWC1-driven changes were inhibited using a large tumor suppressor kinase 1/2 (LATS1/2) inhibitor (TRULI) and small interfering RNA (siRNA). The interaction between the Yes-associated protein (YAP) and the transcriptional enhancer associate domain (TEAD) was inhibited by overexpression of an N/TERT cell line expressing a tetracycline-inducible green fluorescent protein-tagged protein that inhibits YAP-TEAD binding (TEADi). Apoptosis was assessed using cleaved caspase 3/7 and TUNEL staining.

Results: Hippo signaling was the top differentially methylated pathway in SLE versus control keratinocytes. SLE keratinocytes (n = 6) showed significant hypomethylation (Δβ = -0.153) and thus overexpression of the Hippo regulator WWC1 (P = 0.002). WWC1 overexpression increased LATS1/2 kinase activation, leading to YAP cytoplasmic retention and altered proapoptotic transcription in SLE keratinocytes. Accordingly, UVB-mediated apoptosis in keratinocytes could be enhanced by WWC1 overexpression or YAP-TEAD inhibition, mimicking SLE keratinocytes. Importantly, inhibition of LATS1/2 with either the chemical inhibitor TRULI or siRNA effectively eliminated enhanced UVB-apoptosis in SLE keratinocytes.

Conclusion: Our work unravels a novel driver of photosensitivity in SLE: overactive Hippo signaling in SLE keratinocytes restricts YAP transcriptional activity, leading to shifts that promote UVB apoptosis.

Comments:

That's a detailed investigation linking epigenetic modifications and Hippo signaling to the increased susceptibility of SLE keratinocytes to UVB-induced apoptosis. The findings seem to suggest that in SLE patients, hypomethylation and subsequent overexpression of WWC1, a Hippo pathway regulator, lead to heightened activation of LATS1/2 kinase, resulting in altered YAP localization and proapoptotic gene expression in response to UVB.

The experimental approach involving WWC1 overexpression, LATS1/2 inhibition, and YAP-TEAD disruption in cultured keratinocytes, along with the subsequent impact on UVB-induced apoptosis, provides compelling evidence supporting the involvement of the Hippo pathway in this phenomenon.

This study's implications could potentially pave the way for targeted therapies aimed at modulating the Hippo pathway components to mitigate photosensitivity in SLE patients. The inhibition of LATS1/2 effectively curbing enhanced UVB-induced apoptosis in SLE keratinocytes is particularly promising in this regard.

It's fascinating how understanding the molecular mechanisms underlying photosensitivity in SLE could lead to novel therapeutic strategies. This research has shed light on a complex interplay between epigenetics, signaling pathways, and cellular responses, highlighting a potential avenue for therapeutic intervention in SLE-related photosensitivity.