PI3K gamma is the dominant isoform involved in migratory responses of human T lymphocytes: Effects of ex vivo maintenance and limitations of non-viral delivery of siRNA

L D Smith, E S Hickman, R V Parry, J Westwick, S G Ward

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Use of mice in which individual PI3K isoforms have been deleted or mutated by gene targeting, has determined that PI3K gamma provides a key migratory signal for T lymphocyte migration. Since PI3K gamma can be a dispensable signal for directional migration of human T cells, we have adopted a pharmacological and siRNA strategy to assess the contribution of individual PI3K isoforms to chemokine-stimulated migration of human T cells. The broad spectrum PI3K isoform inhibitor Ly294002 inhibits CXCL12-stimulated migration of freshly isolated T lymphocytes. Use of second veneration inhibitors that can discriminate between individual PI3K isoforms, revealed that PI3K gamma was the major contributor to CXCL12-induced migration and PI3K/Akt signaling (as assessed by S6 phosphorylation). Non-viral delivery of siRNA targeting class I (PI3K gamma), class II (PI3KC2 alpha and PI3KC2 beta) and class III PI3Ks, followed by 3 days ex vivo culture, reduces the levels of isoform mRNA, but is insufficient to impact on cell migration responses. However, ex vivo maintenance of T cells alone, independently of siRNA treatment, resulted in the migratory response of T cells toward CXCL 12 becoming insensitive to Ly294002. Remarkably, random migration remains sensitive to Ly294002. This study therefore, highlights that the migratory response of freshly isolated human T cells is dependent on PI3K signals that are provided predominantly by PI3K gamma. However, the role of PI3K in cell migration is context-dependent and diminishes during ex vivo maintenance. (C) 2007 Elsevier Inc. All rights reserved.
Original languageEnglish
Pages (from-to)2528-2539
Number of pages12
JournalCellular Signalling
Volume19
Issue number12
DOIs
Publication statusPublished - 2007

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