p66SHC Promotes Apoptosis and Antagonizes Mitogenic Signaling in T Cells

Abstract

Of the three Shc isoforms, p66Shc is responsible for fine-tuning p52/p46Shc signaling to Ras and has been implicated in apoptotic responses to oxidative stress. Here we show that human peripheral blood lymphocytes and mouse thymocytes and splenic T cells acquire the capacity to express p66Shc in response to apoptogenic stimulation. Using a panel of T-cell transfectants and p66Shc ؊/؊ T cells, we show that p66Shc expression results in increased susceptibility to apoptogenic stimuli, which depends on Ser36 phosphorylation and correlates with an altered balance in apoptosis-regulating gene expression. Furthermore, p66Shc blunts mitogenic responses to T-cell receptor engagement, at least in part by transdominant inhibition of p52Shc signaling to Ras/mitogen-activated protein kinases, in an S36-dependent manner. The data highlight a novel interplay between p66Shc and p52Shc in the control of T-cell fate.

p66SHC promotes T cell apoptosis by inducing mitochondrial dysfunction and impaired Ca2+ homeostasis

“…1 Although the domain organization is identical in the three isoforms, p66Shc not only fails to activate Ras, but competitively inhibits signaling by the other isoforms. [2][3][4] Furthermore, p66Shc is implicated in signaling pathways linking oxidative stress to apoptosis. 5 This property maps to a unique N-terminal domain containing a critical serine residue at position 36, which is phosphorylated in response to stress.…”

“…5 This property maps to a unique N-terminal domain containing a critical serine residue at position 36, which is phosphorylated in response to stress. 4,[6][7][8] Inactivation of the gene encoding p66Shc in the mouse results in prolonged life span, 6 which has been ascribed to a decreased production of reactive oxygen species (ROS). 9,10 Furthermore, p66Shc gene ablation results in protection from oxidative stress-related pathologies in mouse disease models, including high-fat-diet-induced atherogenesis 11 and muscular and endothelial cell apoptosis in acute ischemia.…”

“…Conversely, inactivation of the p66Shc gene protects T cells from dexamethasone-induced apoptosis. 4 Here, we have investigated the mechanisms whereby p66Shc primes T cells to death by the Ca 2 þ ionophore A23187, a potent inducer of apoptosis that causes PTP opening in other systems. 17 We show that p66Shc promotes T cell apoptosis both by triggering cytochrome c release and mitochondrial membrane depolarization, and by impairing Ca 2 þ homeostasis due to downregulation of plasma membrane ATPases and defective Ca 2 þ extrusion.…”

“…We had previously observed that in Jurkat T cells p66Shc displays a basal level of S36 phosphorylation that can be enhanced by a variety of receptor-mediated and pharmacological stimuli including A23187, all of which cause a transient rise of [Ca 2 þ ] c . 4 We hypothesized that the [Ca 2 þ ] c rise could be essential for p66Shc phosphorylation at S36. We therefore measured the effect of A23187, H 2 O 2 and CD3 ligation on p66Shc phosphorylation at S36 in Ca 2 þ -competent cells and after Ca 2 þ depletion by treatment with thapsigargin and EGTA.…”

The small GTPase Rab29 is a common regulator of immune synapse assembly and ciliogenesis

“…Jurkat cell lines stably transfected with pcDNA3.1 (empty vector, ctr) or pcDNA3.1-GtgE (GtgE) were generated as described. 40 GtgE cells were routinely checked for Rab29 depletion by immunoblot. A Jurkat cell line stably transfected with a GFP-tagged Rab29 construct was also generated using pEGFP-Rab29.…”