The calcium-activated chloride channel-associated protein rCLCA2 is expressed throughout rat epidermis, facilitates apoptosis and is downmodulated by UVB

Abstract

The rodent chloride channel regulatory proteins mCLCA2 and its porcine and human homologues pCLCA2 and hCLCA2 are expressed in keratinocytes but their localization and significance in the epidermis have remained elusive. hCLCA2 regulates cancer cell migration, invasion and apoptosis, and its loss predicts poor prognosis in many tumors. Here, we studied the influences of epidermal maturation and UV-irradiation (UVR) on rCLCA2 (previous rCLCA5) expression in cultured rat epidermal keratinocytes (REK) and correlated the results with mCLCA2 expression in mouse skin in vivo. Furthermore, we explored the influence of rCLCA2 silencing on UVR-induced apoptosis. rClca2 mRNA was strongly expressed in REK cells, and its level in organotypic cultures remained unchanged during the epidermal maturation process from a single cell layer to fully differentiated, stratified cultures. Immunostaining confirmed its uniform localization throughout the epidermal layers in REK cultures and in rat skin. A single dose of UVR modestly downregulated rClca2 expression in organotypic REK cultures. The immunohistochemical staining showed that CLCA2 localized in basal and spinous layers also in mouse skin, and repeated UVR induced its partial loss. Interestingly, silencing of rCLCA2 reduced the number of apoptotic cells induced by UVR, suggesting that by facilitating apoptosis, CLCA2 may protect keratinocytes against the risk of malignancy posed by UVB-induced corrupt DNA.

Genomic, biochemical and expressional properties reveal strong conservation of the CLCA2 gene in birds and mammals

“…Concordantly with the high degree of conservation, maCLCA2 is consistently expressed in keratinocytes of stratified epithelia such as those of skin or esophagus and in certain glandular epithelia in all mammals investigated so far ( Braun et al, 2010 ; Connon et al, 2006 ; Connon et al, 2004 ; Erickson, Gruber & Mundhenk, 2020 ; Hamalainen et al, 2021 ; Plog et al, 2012b ; Seltmann et al, 2018 ; Walia et al, 2012 ). It has been proposed that the CLCA2 protein is involved in epithelial differentiation, growth arrest and maturation of keratinocytes ( Connon et al, 2004 ; Koegel & Alzheimer, 2001 ; Ramena et al, 2016 ).…”

CLCA2 overexpression suppresses epithelial-to-mesenchymal transition in cervical cancer cells through inactivation of ERK/JNK/p38-MAPK signaling pathways

“…As a new calcium activated chloride channel protein, CLCA2 plays an important role in tumorigenesis and development. Most studies have shown that there are abnormal expression levels and related signaling pathways of CLCA2 in malignant tumors, and it is closely related to tumor invasion and metastasis [ 7 , 23 , 24 ], CLCA2 is down regulated in cervical cancer [ 25 , 26 ], but its role and exact regulatory mechanism in cervical cancer are still unclear. Our results confirmed that the expression of CLCA2 was significantly decreased in cervical cancer cells.…”

In focus in HCB

“…However, distinct functional species-related differences among the various chloride channel accessory proteins have been reported. Therefore, Hämäläinen et al (2021) have analyzed the expression and possible function of the rat calcium-activated chloride channel-associated protein rCLCA2 in cultured rat epidermal keratinocytes and correlated their findings with the mouse homolog in mouse skin (Fig. 4).…”