Murter Benjamin M, Robinson Sean C, Banerjee Hridesh, Lau Louis, Uche Uzodinma N, Szymczak-Workman Andrea L, Kane Lawrence P
Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Graduate Program in Microbiology and Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
J Biol Chem. 2024 Dec;300(12):107930. doi: 10.1016/j.jbc.2024.107930. Epub 2024 Oct 24.
The protein known as PI3K-interacting protein (PIK3IP1), or transmembrane inhibitor of PI3K (TrIP), is highly expressed by T cells and can modulate PI3K activity in these cells. Several studies have also revealed that TrIP is rapidly downregulated following T cell activation. However, it is unclear how this downregulation is controlled. Using a novel monoclonal antibody that robustly stains cell-surface TrIP, we demonstrate that TrIP is lost from the surface of activated T cells in a manner dependent on the strength of signaling through the T cell receptor and specific downstream signaling pathways, in particular classical PKC isoforms. TrIP expression returns by 24 h after stimulation, suggesting that it may play a role in resetting T cell receptor signaling at later time points. We also provide evidence that ADAM family proteases are required for both constitutive and stimulation-induced downregulation of TrIP in T cells. Finally, by expressing truncated forms of TrIP in cells, we identify the region in the extracellular stalk domain of TrIP that is targeted for proteolytic cleavage.
被称为PI3K相互作用蛋白（PIK3IP1）或PI3K跨膜抑制剂（TrIP）的蛋白质在T细胞中高度表达，并可调节这些细胞中的PI3K活性。多项研究还表明，T细胞激活后TrIP会迅速下调。然而，尚不清楚这种下调是如何被控制的。使用一种能强烈染色细胞表面TrIP的新型单克隆抗体，我们证明TrIP以依赖于通过T细胞受体和特定下游信号通路（特别是经典PKC亚型）的信号强度的方式从活化T细胞表面丢失。刺激后24小时TrIP表达恢复，这表明它可能在后期重置T细胞受体信号中发挥作用。我们还提供证据表明，ADAM家族蛋白酶是T细胞中TrIP组成型和刺激诱导下调所必需的。最后，通过在细胞中表达TrIP的截短形式，我们确定了TrIP细胞外柄结构域中被靶向进行蛋白水解切割的区域。
