RNAi Library Screening Reveals Gβ1, Casein Kinase 2α and ICAP-1 as Novel
Regulators of LFA-1-mediated T-cell Polarity and Migration
Abstract
The αLβ2 integrin LFA-1 plays a key role in T-cell adhesion to the
endothelial vasculature and migration into both secondary lymphoid
organs and peripheral tissues via interactions with its target protein
ICAM-1, but the pathways that regulate LFA-1-mediated T-cell polarity
and migration are not fully understood. In this study we screened two
RNAi libraries targeting G protein-coupled receptors
(GPCR)/GPCR-associated proteins and kinases in a HuT-78 T-cell line
model of LFA-1-stimulated T cell migration. Based on staining of the
actin cytoskeleton, multiple parameters to measure cell morphology were
used to assess the contribution of 1109 genes to LFA-1-mediated T cell
polarity and migration. These RNAi screens identified a number of both
novel and previously identified genes that either increased or decreased
the polarity and migratory capacity of these cells. Following
multiparametric analysis, hierarchical clustering and pathway analysis,
three of these genes were characterised in further detail using primary
human T-cells, revealing novel roles for the heterotrimeric G protein
subunit Gβ1 and casein kinase 2 in LFA-1-mediated T-cell polarity and
migration in-vitro. Our studies also highlighted a new role for ICAP-1,
an adaptor protein previously described to be associated with β1
integrins, in β2 integrin LFA-1-directed migration in T-cells. Knockdown
of ICAP-1 expression in primary T cells revealed a role in cell
polarity, cell velocity and transmigration towards SDF-1 for this
adaptor protein. This study therefore uncovers new roles for
GPCR/GPCR-associated proteins and kinases in T-cell migration and
provides potential novel targets for modulation of the T-cell immune
response