Serine/threonine receptor interacting kinase 4 (RIPK4), which was first identified as a PKC interacting protein, has been characterized as being crucial to epidermal differentiation and homeostasis and mediates multiple key signaling pathways including MAPK, Wnt, and NFκB. However, little is known about the upstream regulators of RIPK4 signaling. Our data suggest that PKCη is a main PKC isoform responsible for activating RIPK4 in keratinocytes. We show that overexpression of PKCη in HEK293T cells is leading to strong phosphorylation of RIPK4 compared to other PKC isoforms, resulting in the typical phospho-RIPK4 protein band in a western blot experiment. Moreover, in vitro knockdown of PKCη in keratinocytes results in almost complete ablation of hyperphosphorylated RIPK4, suggesting RIPK4 activation is dependent on phosphorylation by PKCη. To confirm these findings, an in vitro phosphorylation assay was performed to ensure PKCη is capable of phosphorylating RIPK4 directly. Mass spectrometry was performed to identify PKCη target sites on RIPK4 using a truncated, kinase-dead RIPK4 mutant phosphorylated by PKCη. The sites identified as putative PKCη targets are well conserved and some have been associated with inactivating RIPK4 mutations. Further studies will include functional mutation assays to identify the downstream effects of PKCη-RIPK4 signaling in keratinocytes. Taken together, our results suggest that PKCη plays a key role in RIPK4 activation in epidermal signaling.

ESDR210 - Investigating the PKCη-RIPK4 signaling axis in keratinocytes

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.