Late expression of granulysin by microbicidal CD4+ T cells requires PI3K- and STAT5-dependent expression of IL-2Rbeta that is defective in HIV-infected patients.
Granulysin is a cytolytic effector molecule used by lymphocytes to kill tumor and microbial cells. Regulation of granulysin production is complex. A significant delay (5 days) following stimulation of CD4(+) T cells with IL-2 occurs before granulysin is produced. Unfortunately, the mechanisms responsible for this delay are unknown. We have recently demonstrated that granulysin-mediated killing of Cryptococcus neoformans by CD4(+) T cells is defective during HIV infection. This is because CD4(+) T cells from HIV-infected patients fail to produce granulysin in response to IL-2 activation. The present studies examined the mechanism of delayed production of granulysin and the mechanism of the defect in HIV patients. We demonstrate that IL-2 initially requires both STAT5 and PI3K activation to increase expression of IL-2Rbeta, produce granulysin, and kill C. neoformans. The increased expression of IL-2Rbeta precedes granulysin, and preventing the increased expression of IL-2Rbeta using small interfering RNA knockdown abrogates granulysin expression. Moreover, following the increased expression of IL-2Rbeta, blocking subsequent signaling by IL-2 using IL-2Rbeta-specific blocking Abs abrogates expression of granulysin. Finally, CD4(+) T cells from HIV-infected patients, who are defective in both STAT5 and PI3K signaling, fail to express IL-2Rbeta and fail to produce granulysin. These results suggest that IL-2 signals via PI3K and STAT5 to increase expression of IL-2Rbeta, which in turn is required for production of granulysin. These results provide a mechanism to explain the "late" production of granulysin during normal T cell responses, as well as for defective granulysin production by CD4(+) T cells in HIV-infected patients.
Zheng
Chun Fu
CF
Department of Microbiology and Infectious Disease, University of Galgary, Alberta, Canada.
Jones
Gareth J
GJ
Shi
Meiqing
M
Wiseman
Jeremy C D
JC
Marr
Kaleb J
KJ
Berenger
Byron M
BM
Huston
Shaunna M
SM
Gill
M John
MJ
Krensky
Alan M
AM
Kubes
Paul
P
Mody
Christopher H
CH
D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D058544:Class Ib Phosphatidylinositol 3-Kinase; D003455:Cryptococcus neoformans / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015658:HIV Infections / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology / Q000378:metabolism; D053646:Interleukin-2 Receptor beta Subunit / Q000276:immunology / Q000378:metabolism*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D050799:STAT5 Transcription Factor / Q000032:analysis / Q000378:metabolism*; D015398:Signal Transduction
D000945:Antigens, Differentiation, T-Lymphocyte; D058544:Class Ib Phosphatidylinositol 3-Kinase; D004791:Enzyme Inhibitors; D007376:Interleukin-2; D053646:Interleukin-2 Receptor beta Subunit; D007527:Isoenzymes; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D050799:STAT5 Transcription Factor; C075005:GNLY protein, human; C508020:IL2RB protein, human; C546760:PIK3CG protein, human