Increases in transmembrane glycoprotein NMB (GPNMB), phospho‐ERK1/2, and matrix metallopeptidase (MMP)‐9 follow decline in arylsulfatase B in cystic fibrosis

Abstract

In previous reports, decline in the enzyme arylsulfatase B (ARSB; N‐acetylgalactosamine‐ 4‐sulfatase) was identified in cystic fibrosis (CF) cells in culture and in circulating leukocytes from CF patients. Recently, the transmembrane glycoprotein NMB (GPNMB) was shown to be increased in a CF gene array and in Arylsulfatase B (ARSB; N‐acetylgalactosamine‐4‐sulfatase)‐null mice. These findings are consistent with previous reports that ARSB is reduced in cystic fibrosis (CF). A mechanism by which decline in ARSB, and the resultant increase in chondroitin 4‐sulfate, increased GPNMB expression has been reported. Subsequently, experiments were designed to assess the potential role of GPNMB in CF and the mechanisms by which GPNMB might contribute to CF pathophysiology. In serum and circulating leukocytes from CF and control patients, GPNMB levels were determined by ELISA. GPNMB was also measured in cells and spent media of CFTR‐corrected, CFTR‐uncorrected, and normal human bronchial epithelial cells (BEC) following ARSB siRNA or control siRNA. The GPNMB which co‐immunoprecipitated with β‐1 integrin was determined by ELISA. Matrix metalloproteinase (MMP)‐9 was measured, and the correlations between GPNMB and MMP‐9 in serum and spent media were determined. Phospho‐ERK1/2 in the circulating leukocytes and in the cultured cells was measured. The impact of excess exogenous RGD peptide and GPNMB siRNA on phospho‐ERK1/2 content was determined, and the impact of the RGD peptide, GPNMB siRNA, and ERK phosphorylation inhibitor on MMP‐9 mRNA expression was determined. GPNMB was markedly increased in cells and serum of CF patients compared to controls (p<0.0001, unpaired t‐test, two‐tailed). In uncorrected CF cells and in BEC following ARSB silencing, the GPNMB was significantly increased (p<0.0001; p<0.001). Silencing GPNMB or treatment with excess RGD peptide significantly inhibited the ARSB‐silencing induced increase in phospho‐ERK1/2 in the BEC. Silencing GPNMB, treatment with excess RGD peptide, or treatment with ERK phosphorylation inhibitor blocked the ARSB silencing‐induced increases in MMP‐9 expression in the normal BEC. Findings suggest that decline in ARSB activity caused by decline in CFTR function leads to increased GPNMB, phospho‐ERK1/2, and MMP‐9 expression, which may contribute to disruption of cell signaling and to organ dysfunction in CF.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.