To further explore how PALS1 impacts on lymphocyte proliferation, early signaling pathways emanating from the TCR were examined in Jurkat cells transfected with PALS1 siRNA. We did not detect major alteration in the general pattern of tyrosine phosphorylation, or mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinases (ERK) 1/2 phosphorylation upon TCR stimulation ( Figure 3A ). Only a slight but consistent increase in TCR-mediated phosphorylation of p38 was noted ( Figure 3A ). Moreover, CD3-induced calcium mobilization was largely normal in PALS1-knockdown Jurkat cells ( Figure 3B ).