Abstract
Background
In the gastrointestinal (GI) tract, goblet cells secrete MUC2 that makes up the mucus layer critical in innate host defense in separating the microbiota from the single layer of intestinal epithelial cells. Associated with MUC2 mucin are other mucus-associated proteins (mucus APs) including calcium-activated chloride channel regulator 1 (CLCA1), Fc fragment of IgG binding protein (FCGBP) and kallikrein 1 (KLK1). These proteins are hypothesized to be important in stabilizing MUC2 and aiding in its protective functions but are not well characterized. Goblet cells also produce various innate host defense molecules including trefoil factor 3 (TFF3) and resistin-like molecule b (RELMb) and its unclear how these proteins interact with MUC2 to enhance innate host defences.
Aims
1. To determine if MUC2 and mucus associated proteins is differentially regulated.
2. To interrogate if a common intracellular signaling pathway can regulate MUC2, TFF3 and RELMb expression and secretion in vitro and in vivo.
Methods
In this study, I quantified MUC2, APs, TFF3 and RELMb expression in LS174T goblet cells basally and in response to the colonic pathogen Entamoeba histolytica (Eh) and various mucus secretagogues by Q-PCR and Western Blots.
Results
Goblet cell proteins were developmentally regulated that coincided with maturation of the goblet cell phenotype at days 5 to 6. Cells stimulated with known mucus seretagogues that use unique signalling pathways such as PMA (PKC activator) and PGE2 (cAMP signalling), simultaneously increased MUC2, mucus APs, TFF3 and RELMb expression. However, in response to Eh, there was a time-dependent expression of MUC2 and enhanced expression of RELMb while mucus APs and TFF3 were unaffected. I next determined if deficiency in Muc2-/- affected the expression of goblet cell innate defense proteins as compared to Muc2+/+ littermates. Surprisingly, there were no significant changes in goblet cell proteins or mucus APs suggesting no negative feedback of these molecules in the absence of Muc2.
Conclusions
This research demonstrates that MUC2, mucus APs and goblet cells peptides are developmentally regulated and use common signalling pathways in innate host defense.
Funding Agencies
CIHR