Investigation of the Role of Phosphoinositide Lipid Kinases and Phosphatases in T Lymphocyte Biology

Abstract

PI3K mediated signalling is crucial for various lymphocyte functions.Pharmacological targeting of PI3K is therefore an attractive target fortherapeutic intervention in a range of inflammatory disorders as well ascancer. PI3K mediated signalling is regulated by the actions of lipidphosphatases, whilst pharmacological targeting of these lipid phosphatasesoffers an alternative means with which to modulate PI3K mediated signalling.This thesis aimed to utilise novel pharmacological compounds to probe therole of PI3K and the lipid phosphatases SHIP-1 and SHIP-2 in primary humanT lymphocytes. The acute inhibition of PI3Kδ activity was shown to inhibit thesecretion of IL-17A by human T lymphocytes. In contrast, the prolongedinhibition of PI3Kδ activity or the down-regulation of PI3Kδ expression inprimary human T lymphocytes resulted in increased secretion of IL-17A. Anallosteric activator of SHIP-1 was shown to inhibit chemokine mediatedsignalling and in vitro T cell motility. Activation of SHIP-1 also inhibited TCRmediated Akt phosphorylation, proliferation and cytokine secretion. SHIP-1activation reduced the affinity state of LFA-1 and abrogated the ability ofprimary human T lymphocytes to adhere to fibronectin and ICAM1.Pharmacological inhibition of SHIP-1 activity also reduced chemokinemediated signalling and motility. In addition, SHIP-1 inhibition reduced TCRmediated signalling and adhesion. The reported SHIP-2 inhibitorBiPh(2,3’,4,5’,6)P5 was shown to inhibit the activity of SHIP-1 with equalpotency as the inhibition of SHIP-2 activity. Pharmacological inhibition ofSHIP-2 activity alone showed little effect on primary human T lymphocytefunction, indicating that SHIP-1 is the primary SHIP protein involved in Tlymphocyte function.In addition, this thesis showed that the expression and activity of the lipidphosphatase INPP4b is not lost in leukemic cell lines. INPP4b was howeverfound to be down-regulated in Th17 polarised cells, indicating a possible rolefor INPP4b in Th17 differentiation.

Date of Award	25 Jul 2013
Original language	English
Awarding Institution	University of Bath
Supervisor	Stephen Ward (Supervisor)