The role of the Coxsackie and Adenoviral Receptor in TNF alpha driven inflammation

Abstract

Transepithelial migration (TEpM) of leucocytes during the inflammatory process requires engagement with receptors expressed on the basolateral surface of the epithelium. One such receptor is Coxsackie and Adenovirus Receptor (CAR) which binds to Junction Adhesion Molecule - L (JAM-L) on leucocytes during TEpM.
This study reports the first evidence that TEpM of leucocyte cells requires, and is controlled by, phosphorylation of the cytoplasmic tail of CAR. The in vitro data shows that these leucocyte cells can adhere to an epithelial layer but where the cytoplasmic tail of CAR is prevented from undergoing phosphorylation the leucocytes are unable to transmigrate. Furthermore it shows that this CAR phosphorylation step is driven by TNF α signalling via a TNFR1-PI3K-PKCδ dependent signalling pathway. The work demonstrates that THP-1 cells can secrete TNF α thereby activating the CAR phosphorylation pathway leading to TEpM without addition of exogenous TNF α but importantly where TNF α is added this process is augmented suggesting a role for CAR in inflammatory conditions. Mouse models also confirm that CAR phosphorylation in response to inflammatory stimuli occur in vivo. Both acute (a 24 hour inhaled TNF α challenge) and chronic (a 34 day ovalbumin challenge) inflammatory conditions are studied. Confocal microscopy techniques are used to show that the cytoplasmic tail of CAR is phosphorylated. Specifically this is seen at the cell membrane of epithelial cells of bronchioles with associated inflammatory cells in the interstitium.
Taken together these data describe a novel method for the control of TEpM by transmigrating leucocytes that can also be heightened by the presence of proinflammatory cytokines during inflammation. This provides a novel target for controlling inflammation at the epithelium, a key component of the pathogenesis of many diseases including asthma.

Date of Award	2016
Original language	English
Awarding Institution	King's College London
Supervisor	George Santis (Supervisor) & Madeline Parsons (Supervisor)