Defining a role for lung function associated gene GSTCD in cell homeostasis

Amanda P Henry,Kelly Probert,Sangita Bhaker,Sheyda Azimi,Ian P Hall,Dhruma Thakker,Ceri E Stewart,Ian Sayers

doi:10.1186/s12931-019-1146-3

Abstract

Genome wide association (GWA) studies have reproducibly identified signals on chromosome 4q24 associated with lung function and COPD. GSTCD (Glutathione S-transferase C-terminal domain containing) represents a candidate causal gene in this locus, however little is currently known about the function of this protein. We set out to further our understanding of the role of GSTCD in cell functions and homeostasis using multiple molecular and cellular approaches in airway relevant cells. Recombinant expression of human GSTCD in conjunction with a GST activity assay did not identify any enzymatic activity for two GSTCD isoforms questioning the assignment of this protein to this family of enzymes. Protein structure analyses identified a potential methyltransferase domain contained within GSTCD, with these enzymes linked to cell viability and apoptosis. Targeted knockdown (siRNA) of GSTCD in bronchial epithelial cells identified a role for GSTCD in cell viability as proliferation rates were not altered. To provide greater insight we completed transcriptomic analyses on cells with GSTCD expression knocked down and identified several differentially expressed genes including those implicated in airway biology; fibrosis e.g. TGFBR1 and inflammation e.g. IL6R. Pathway based transcriptomic analyses identified an over-representation of genes related to adipogenesis which may suggest additional functions for GSTCD. These findings identify potential additional functions for GSTCD in the context of airway biology beyond the hypothesised GST activity and warrant further investigation.

Highlights

Lung function forms a key diagnostic criteria for chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality
Two vectors expressing different isoforms of human Glutathione S-transferase C-terminal domain containing (GSTCD) were transfected into two human airway cell types: airway smooth muscle (HASM) and bronchial epithelial cells (HBECs) alongside transfection of the positive control Glutathione STransferase (GST) Mu5 (GSTM5)
The Sensolyte GST activity assay was performed on these recombinant cells, results revealed no discernible change in GST activity in either GSTCD variant 1 or 2 cells (Fig. 1)

Summary

Introduction

Lung function forms a key diagnostic criteria for chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality. More recent studies replicated association with variants spanning GSTCD and forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and COPD [5,6,7,8,9,10,11,12]. These variants have recently been associated with FEV1 in children and with growth, measured as bronchial responsiveness development [13], suggesting that GSTCD may have an early life effect. GSTCD represents a potential candidate/casual gene in this region and may functionally contribute to the development or severity of COPD

Methods

Results

Discussion

Conclusion