Biased binding of class IA phosphatidyl inositol 3-kinase subunits to inducible costimulator (CD278)

Abstract

To better understand T lymphocyte costimulation by inducible costimulator (ICOS; H4; CD278), we analyzed proteins binding to ICOS peptides phosphorylated at the Y(191)MFM motif. Phosphorylated ICOS binds class IA phosphatidyl inositol 3-kinase (PI3-K) p85α, p50-55α and p85β regulatory subunits and p110α, p110δ and p110β catalytic subunits. Intriguingly, T cells expressed high levels of both p110α or p110δ catalytic subunits, yet ICOS peptides, cell surface ICOS or PI3-kinase class IA regulatory subunits preferentially coprecipitated p110α catalytic subunits. Silencing p110α or p110δ partially inhibited Akt/PKB activation induced by anti-CD3 plus anti-ICOS antibodies. However, silencing p110α enhanced and silencing p110δ inhibited Erk activation. Both p110α- and p110δ-specific inhibitors blocked cytokine secretion induced by TCR/CD3 activation with or without ICOS costimulus, but only p110α inhibitors blocked ICOS-induced cell elongation. Thus, p110α and p110δ are essential to optimal T cell activation, but their abundance and activity differentially tune up distinct ICOS signaling pathways.

Characteristics of TCR/CD3 complex CD3ɛ chains of regulatory CD4+ T (Treg) lymphocytes: role in Treg differentiation in vitro and impact on Treg in vivo

“…In contrast, differences between Tconv and Tregs were negligible for the LAT adaptor, the p38 MAPK, and the p85 regulatory subunit of Class IA PI3K. We have observed by qRT-PCR that p110␣ and p110␦␦ are the main Class IA PI3K catalytic subunits expressed by CD4 ϩ T cells [39]. As p110␦ is functionally important to Tregs [40,41], and p110␣ might regulate Treg differentiation negatively through the activation of the PKB and mTOR kinases [42][43][44], the abundance of the p110␣ and p110␦ catalytic subunits was also determined.…”

PI3K signalling in B- and T-lymphocytes: new developments and therapeutic advances

“…It is also possible that PI3K isoforms other than p110δ might contribute to ICOS signaling. Using synthetic ICOS peptides and ICOS immunoprecipitations, a significant amount of p110α bound to ICOS can be detected after stimulation of the CD4 T cell line D10 and primary CD4 T cell blasts [143]. siRNA-mediated knockdown or pharmacological inhibition of p110α partially reduces ICOS-dependent AKT phosphorylation in D10 cells.…”

Dissociation of actin polymerization and lipid raft accumulation by ligation of the Inducible Costimulator (ICOS, CD278)

“…B7 h, anti-ICOS antibodies) adsorbed to solid substrates induce PI-3 kinase-dependent changes in the actin cytoskeleton leading to T cell elongation and filopodia formation. [38][39][40] Furthermore, our previous data show that it is the p110␣ catalytic isoform of PI3-kinase that is primarily involved in this phenomenon. 38 We show here that in D10 cells, elongation is accompanied by cell spreading with distinct lamellipodia-and filopodia-like structures (Fig.…”

“…through Filamin-A, yet it is still capable of inducing clear changes in T cell shape mediated by p110␣ PI3-kinase activation of actin polymerization (see, 38 and Fig. 1).…”

“…37 Lastly, ICOS ligand bound to flat surfaces induces PI-3K-dependent re-organization of the actin cytoskeleton producing elongation of T cells expressing ICOS. [38][39][40] However, there are data either against 38,39 or in favour 40 of a role for Akt. There are also data showing a role for Rho family members like Rac and Cdc42, in ICOS-mediated T cell elongation ( 40 ; Acosta, Y., Rojo, J.M.…”