title: Wnt5a/β-catenin signaling drives calcium-induced differentiation of human primary keratinocytes.
abstract: It is well established that a gradient of extracellular calcium within the epidermis regulates the differentiation of keratinocytes. However, the molecular mechanisms implicated in this process are not fully understood. RNA interference of the calcium-sensing receptor (CaSR) showed that CaSR is essential in calcium-induced differentiation of normal human epidermal keratinocytes (NHEKs) by increasing the levels of free intracellular calcium, which upregulates the expression of Wnt5a but not Wnt3a, Wnt4, and Dkk-1 in the cells. Subsequently, autocrine Wnt5a promotes the differentiation of NHEKs, determined by increased biosynthesis of keratin-1 and loricrin, whereas proliferation is suppressed. Addition of both Wnt5a and calcium to NHEKs activated the Wnt/β-catenin signaling pathway as indicated by (i) increased stability of β-catenin in the cells, (ii) enhanced β-catenin transcriptional activity, demonstrated by a luciferase-based β-catenin-activated reporter assay, and (iii) augmented Wnt/β-catenin target gene expression. NHEKs depleted for β-catenin had a significantly reduced susceptibility to calcium-induced differentiation. Knockdown of axin 2, an antagonist of β-catenin stability, enhanced the biosynthesis of keratin-1 and loricrin in the cells. Our findings establish a directional crosstalk between CaSR and Wnt/β-catenin signaling in keratinocyte differentiation via Wnt5a that acts as an autocrine stimulus in this process.
authors.affiliation: Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Popp
authors.affiliation: Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Steinritz
authors.affiliation: Walther-Straub-Institute of Pharmacology and Toxicology, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Breit
authors.affiliation: Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Janina
authors.initials: J
authors.lastname: Deppe
authors.affiliation: Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Virginia
authors.initials: V
authors.lastname: Egea
authors.affiliation: Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany; Molecular and Cellular Sport Medicine, German Sport University, Cologne, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Schmidt
authors.affiliation: Walther-Straub-Institute of Pharmacology and Toxicology, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gudermann
authors.affiliation: Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Weber
authors.affiliation: Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Munich, Germany. Electronic address: christian.ries@med.uni-muenchen.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Ries
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D006801:Humans; D015603:Keratinocytes / Q000166:cytology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D044169:Receptors, Calcium-Sensing / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins / Q000502:physiology*; D000071818:Wnt-5a Protein; D051176:beta Catenin / Q000502:physiology*
chemical_list: C095550:CASR protein, human; C495270:CTNNB1 protein, human; D011518:Proto-Oncogene Proteins; D044169:Receptors, Calcium-Sensing; C085389:WNT5A protein, human; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D051176:beta Catenin; D002118:Calcium