Stromal cell-derived factor 1-alpha (SDF)-induced human T cell chemotaxis becomes phosphoinositide 3-kinase (PI3K)-independent: role of PKC-theta.
Stromal cell-derived factor 1alpha (SDF-1alpha) is the exclusive ligand for the chemokine receptor CXCR4. This receptor plays a pivotal role in immune responses, the pathogenesis of infection such as HIV, and cellular trafficking. However, the signaling mechanisms regulating SDF-driven T cell migration are not well defined. In this study, we determined the role of PI3K and protein kinase C- theta (PKC-theta) in SDF-induced human T cell migration in fresh versus cultured T cells. Purified human T cells (fresh vs. 48 h in media, unstimulated or activated by anti-CD3+anti-CD28) were used. Western blots showed that SDF induced phospho-(p)-Akt [threonine (Thr)308 and serine 473], a proxy for PI3K activity, in fresh cells and p-PKC-theta in 48 h unstimulated cells. LY294002 (PI3K inhibitor) reduced SDF-induced chemotaxis in fresh cells by 51%, whereas it minimally affected chemotaxis in 48 h unstimulated or activated cells. However, a specific PKC-theta inhibitor, pseudosubstrate for PKC-theta, reduced chemotaxis in 48 h unstimulated and stimulated T cells by 72% and 87%, respectively. Thus, chemotaxis becomes independent of PI3K signaling in human T cells cultured for 48 h. Under these conditions, PKC-theta is phosphorylated (Thr538) by SDF, and chemotaxis becomes largely PKC-theta-dependent.
University of Tennessee Health Science Center, 874 Union Avenue, Memphis, TN 38163, USA.
Nahid A
NA
Shahabi
K
K
McAllen
Burt M
BM
Sharp
D018929:Cell Culture Techniques; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D054377:Chemokine CXCL12 / Q000494:pharmacology*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D017154:Stromal Cells / Q000502:physiology; D013601:T-Lymphocytes / Q000187:drug effects / Q000502:physiology*
D054377:Chemokine CXCL12; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; C076233:PRKCQ protein, human