N. Selliah et al., PROTEOLYTIC CLEAVAGE OF ALPHA-ACTININ BY CALPAIN IN T-CELLS STIMULATED WITH ANTI-CD3 MONOCLONAL-ANTIBODY, The Journal of immunology, 156(9), 1996, pp. 3215-3221
Stimulation of the TCR/CD3 complex on T cells initiates rearrangement
of the actin cytoskeleton. The results presented show that a temporal
increase in the appearance of filamentous actin begins immediately aft
er stimulation of T cells with immobilized anti-CD3 mAb. The formation
of filamentous actin in these stimulated cells reaches a steady state
within 30 min after anti-CD3 mAb stimulation. At this time, pseudopod
formation is observed and becomes progressively more evident over the
next several hours. Experiments were done to investigate the role of
the actin cytoskeletal associated proteins, alpha-actinin, vinculin, a
nd talin, in the assembly of the actin cytoskeleton in anti-CD3 mAb-st
imulated T cells. Using immunofluorescence, these three proteins are d
etected throughout the cytosol in resting T tells. However, after anti
-CD3 mAb stimulation of the T cells, these proteins move to one pole o
f the cell. Electrophoresis followed by immunoblotting of T cell lysat
es prepared from resting as well as anti-CD3 mAb-stimulated cells reve
aled that alpha-actinin, but not vinculin or talin, was modified as a
consequence of cell activation. Results show that alpha-actinin exists
as a 105-kDa subunit in resting T cells, but that anti-CD3 mAb stimul
ation of T cells leads to the appearance of an 80-kDa lower molecular
form of alpha-actinin. Experiments show that this occurs as a conseque
nce of the 105-kDa subunit being proteolytically cleaved by calpain.