Murine CLCA5 is uniquely expressed in distinct niches of airway epithelial cells

Abstract

The murine mCLCA5 protein is a member of the chloride channel regulators, calcium-activated (CLCA) family and is suspected to play a role in airway mucus cell differentiation. Although mCLCA5 mRNA was previously found in total lung extracts, the expressing cells and functions in the naive murine respiratory tract are unknown. Therefore, mCLCA5 protein expression was identified by immunohistochemistry and confocal laser scanning microscopy using entire lung sections of naive mice. Moreover, we determined mRNA levels of functionally related genes (mClca3, mClca5, Muc5ac and Muc5b) and quantified mCLCA5-, mCLCA3- and CC10-positive cells and periodic acid-Schiff-positive mucus cells in naive, PBS-treated or Staphylococcus aureus-infected mice. We also investigated mCLCA5 protein expression in Streptococcus pneumoniae and influenza virus lung infection models. Finally, we determined species-specific differences in the expression patterns of the murine mCLCA5 and its human and porcine orthologs, hCLCA2 and pCLCA2. The mCLCA5 protein is uniquely expressed in highly select bronchial epithelial cells and submucosal glands in naive mice, consistent with anatomical locations of progenitor cell niches. Under conditions of challenge (PBS, S. aureus, S. pneumoniae, influenza virus), mRNA and protein expression strongly declined with protein recovery only in models retaining intact epithelial cells. In contrast to mice, human and porcine bronchial epithelial cells do not express their respective mCLCA5 orthologs and submucosal glands had fewer expressing cells, indicative of fundamental differences in mice versus humans and pigs.

The Goblet Cell Protein Clca1 (Alias mClca3 or Gob-5) Is Not Required for Intestinal Mucus Synthesis, Structure and Barrier Function in Naive or DSS-Challenged Mice

“…However, its expressing cell type is unknown to date. The Clca2 protein which is expressed in keratinocytes of stratified epithelia and in distinct niches of the respiratory tract [ 48 , 74 ] has not been detected in the intestinal tract to date which is consistent with our findings [ 48 ]. The absence of any differential Clca expression pattern in the mucus on the protein level suggests that the lack of a phenotype may not be due to a phenotype rescue by other Clca homologs.…”

Stat3 modulates chloride channel accessory protein expression in normal and neoplastic mammary tissue

“…Other investigators have suggested that CLCA proteins may act as extracellular signalling molecules 17, 36 and it is tempting to speculatively attribute such as role to mCLCA5 in this context at the invasive edge of the tumour (Figure 7). …”

“…17 Of particular interest, both CLCA2 and CLCA4 have been shown to inhibit proliferation of breast cancer cells when ectopically expressed in vitro , 18 whereas normal breast tissue exhibits high levels of CLCA2 in both acini and small ducts. 19 Murine CLCA5 (mCLCA5) is highly homologous to human CLCA2 (hCLCA2) and is considered to be its orthologue.…”

The Mammary Microenvironment in Mastitis in Humans, Dairy Ruminants, Rabbits and Rodents: A One Health Focus

“…A positive association is observed between murine CLCA1 and CLCA2 and Stat3 activity, whilst Stat3 negatively regulates murine CLCA5, the murine orthologue of human CLCA2 [ 125 ]. The exact functions of CLCA family members within the mammary gland are yet to be determined, but their regulation by Stat3 during the involution period may be pertinent to the pathogenesis of involution-associated mastitis given their postulated modulation of the innate immune response and/or potential activity as signalling molecules [ 126 , 127 ].…”