ARNT controls the expression of epidermal differentiation genes through HDAC- and EGFR-dependent pathways

Abstract

SummaryPreviously we showed that spatial and developmental modulation of ARNT (HIF1b) expression in mouse epidermis is essential for maintenance of keratinocyte differentiation, proper formation of the barrier and normal desquamation. Here, using lentiviral suppression or induction of ARNT in TERT-immortalized (N-TERT) and HaCaT cells we assessed the nature and mechanisms of ARNT involvement in control of differentiation in human epidermal keratinocytes. ARNT depletion did not affect the levels of basal keratins K5 and K14, but significantly induced expression of several key differentiation markers (an effect abolished by EGF supplementation). Furthermore, ARNT deficiency resulted in the downregulation of amphiregulin (AREG) -the most highly expressed EGFR ligand in human keratinocytes -whereas upregulation of ARNT showed the opposite. In ARNT-deficient monolayer cultures and 3D epidermal equivalents, the downregulation of AREG was concurrent with a decline of EGFR and ERK1/2 phosphorylation. TSA, a potent suppressor of HDAC activity, abolished the effects of ARNT deficiency, implying a role for HDACs in ARNT-dependent modulation of the AREG-EGFR pathway and downstream epidermal genes. Total HDAC activity was significantly increased in ARNT-depleted cells and decreased with ARNT overexpression. ARNT-dependent shifts in HDAC activity were specifically attributed to significant changes in the levels of HDAC1, HDAC2 and HDAC3 proteins (but not mRNA) in both monolayer and 3D cultures. Collectively, our results suggest that ARNT controls AREG expression and the downstream EGFR-ERK pathway in keratinocytes, at least in part, by modulating HDAC activity. This novel regulatory pathway targeting advanced stages of epidermal differentiation might have important implications for skin pathology such as psoriasis, atopic dermatitis and cancer.

Comprehensive Bioinformation Analysis of the MRNA Profile of Fascin Knockdown in Esophageal Squamous Cell Carcinoma

“…Consistent with our previous results, fascin transcription may be subjected to the regulation of the EGF/EGFR signaling pathway (Robertson et al, 2012). ZNF42 (also named Myeloid zinc finger 1, MZF1) belongs to the Kruppel family of zinc finger transcription factors, has been found bided to the Axl promoter, transactivated promoter activity, and enhanced Axl-mRNA and protein expression in a dose-dependent manner.…”

Coal tar induces AHR-dependent skin barrier repair in atopic dermatitis

“…Genetic approaches in mice, however, have also revealed that AHR signaling plays a role in epidermal pathophysiology. Deficiency or constitutive expression of AHR interaction partners ARNT (44,45) and NRF2 (46), respectively, has detrimental effects on epidermal differentiation and barrier function, whereas AHR transgenic mice develop inflammatory skin lesions with hyperkeratinization (47). All these studies show that disturbance of normal AHR signaling, either by genetic approaches or TCDD exposure, leads to epidermal abnormalities.…”

The EGF receptor ligand amphiregulin controls cell division via FoxM1

“…19–22 EGFR becomes activated in response to binding members of the EGF ligand family, 23 several of which are expressed in human keratinocytes and skin including amphiregulin (AREG), betacellulin, epigen, epiregulin, heparin-binding EGF-like growth factor (HB-EGF), and transforming growth factor-alpha (TGF-a). 7,24,25 Metalloproteinase-mediated cleavage of the transmembrane precursors of these growth factors is thought to be required for major EGFR ligand functions including cell proliferation and migration. 23 …”