A novel DLX3–PKC integrated signaling network drives keratinocyte differentiation

Abstract

Epidermal homeostasis relies on a well-defined transcriptional control of keratinocyte proliferation and differentiation, which is critical to prevent skin diseases such as atopic dermatitis, psoriasis or cancer. We have recently shown that the homeobox transcription factor DLX3 and the tumor suppressor p53 co-regulate cell cycle-related signaling and that this mechanism is functionally involved in cutaneous squamous cell carcinoma development. Here we show that DLX3 expression and its downstream signaling depend on protein kinase C α (PKCα) activity in skin. We found that following 12-O-tetradecanoyl-phorbol-13-acetate (TPA) topical treatment, DLX3 expression is significantly upregulated in the epidermis and keratinocytes from mice overexpressing PKCα by transgenic targeting (K5-PKCα), resulting in cell cycle block and terminal differentiation. Epidermis lacking DLX3 (DLX3cKO), which is linked to the development of a DLX3-dependent epidermal hyperplasia with hyperkeratosis and dermal leukocyte recruitment, displays enhanced PKCα activation, suggesting a feedback regulation of DLX3 and PKCα. Of particular significance, transcriptional activation of epidermal barrier, antimicrobial peptide and cytokine genes is significantly increased in DLX3cKO skin and further increased by TPA-dependent PKC activation. Furthermore, when inhibiting PKC activity, we show that epidermal thickness, keratinocyte proliferation and inflammatory cell infiltration are reduced and the PKC-DLX3-dependent gene expression signature is normalized. Independently of PKC, DLX3 expression specifically modulates regulatory networks such as Wnt signaling, phosphatase activity and cell adhesion. Chromatin immunoprecipitation sequencing analysis of primary suprabasal keratinocytes showed binding of DLX3 to the proximal promoter regions of genes associated with cell cycle regulation, and of structural proteins and transcription factors involved in epidermal differentiation. These results indicate that Dlx3 potentially regulates a set of crucial genes necessary during the epidermal differentiation process. Altogether, we demonstrate the existence of a robust DLX3-PKCα signaling pathway in keratinocytes that is crucial to epidermal differentiation control and cutaneous homeostasis.

Homeobox transcription factor DLX4 is not necessary for skin development and homeostasis

“…We previously reported that epidermal Dlx3 deletion results in hyperproliferation, which is exacerbated with TPA treatment . We tested the effect of TPA treatment on DLX4 KO skin and detected no difference between WT and Dlx4 KO as assessed by morphology and quantification of epidermal thickness (Figure E,F).…”

A de novo germline mutation of DLX3 in a Brown Swiss calf with tricho‐dento‐osseus‐like syndrome

“…Six different dominant acting DLX3 mutations causing TDO with marked phenotypic variability have been reported in humans . The most common mutation in DLX3 is a frameshift mutation (c.571_574delGGGG), resulting in recoding and truncating the C‐terminal transactivating domain of the DLX3 protein (p.Gly191ArgfsTer66) . Human TDO may be caused by loss of function and haploinsufficiency of DLX3 .…”

s-HBEGF/SIRT1 circuit-dictated crosstalk between vascular endothelial cells and keratinocytes mediates sorafenib-induced hand–foot skin reaction that can be reversed by nicotinamide

“…Hyper-keratosis, including hyper-proliferation and hyper-differentiation, arises from the epidermal dyshomeostasis in keratinocytes. [16][17][18][19] Given that most cutaneous toxicities induced by drugs (e.g., everolimus, adriamycin liposome, and capecitabine) are caused by cellular processes targeting keratinocytes, [20][21][22] we initially sought to test the direct effect of sorafenib on keratinocytes by employing human primary keratinocytes and HaCaT cells, the immortalized human keratinocytes which largely retained the differentiation capacity of normal epidermal cells. 24 We examined the states of proliferation and differentiation in keratinocytes, with keratin 5 (KRT5) and keratin 14 (KRT14) applied as proliferation markers, and keratin 1 (KRT1), keratin 10 (KRT10), loricrin (LORICRIN) and involucrin (IVL) characterizing differentiation.…”

“…[12][13][14][15] Hyper-keratosis, defined as stratum corneum thickening, generally results from the abnormality in epidermal homeostasis of keratinocytes, including hyperproliferation and hyper-differentiation. [16][17][18][19] Since numerous studies have uncovered that most drug-induced cutaneous toxicities are the aftereffects of pathways directly affecting keratinocytes, [20][21][22] keratinocyte dysfunction has thus been largely speculated as the main cause of sorafenib-induced HFSR. However, intervention strategies based on such concept are proven ineffective.…”