TCR-Associated Rasal1 rewires T-cell mitochondrial metabolism to regulate checkpoint immunotherapy

Introduction/Rationale: Rasal1, a GTPase-activating protein, is a novel component of the T-cell receptor (TCR) complex that associates with ZAP-70 and negatively regulates the p21ras/ERK pathway (Thaker et al., Nat. Commun., PMID: 31641113). Here, we demonstrate that Rasal1 selectively regulates mitochondrial oxidative phosphorylation (OXPHOS) metabolism, while cooperating with anti–PD–1 therapy to limit T-cell exhaustion.

Methods: Utilizing a knock-in mutant mouse expressing Rasal1 lacking the C2-1 domain (Rasal1c-mut), we analyzed glycolytic- and mitochondrial-driven metabolic programme by measuring the oxygen consumption rate (OCR), and the extracellular acidification rate (ECAR). In vivo studies were conducted in Rasal1c-mut mice using several immune checkpoint blockade (ICB)-resistant melanoma, colorectal, lymphoma, and lung carcinoma models in response to anti–PD–1 treatment.

Results: Primary T cells from mice expressing impaired Rasal1 exhibited a normal glycolytic shift following antigen stimulation but displayed a pronounced and selective increase in mitochondrial respiration. These findings indicate that Rasal1 fine-tunes TCR-dependent mitochondrial activity to sustain ATP generation and biosynthetic output during activation. Unexpectedly, inactive Rasal1—with elevated ZAP-70 and ERK signaling—synergized with anti–PD-1 blockade to reduce tumor-infiltrating lymphocyte exhaustion and promote the expansion of CD8⁺PD-1⁺TCF1⁺ stem-like progenitor cells, leading to enhanced tumor control. The same mechanism also increased the presence of cytolytic CD4⁺ TILs.

Conclusion: Collectively, our data reveal Rasal1 as a unique metabolic brake in T cells whose modulation offers a promising strategy to enhance the durability and breadth of immune checkpoint therapies.