Structure and Mechanisms of Mitochondrial Pyruvate Carrier (MPC) - Project Summary/Abstract Pyruvate, a key product of glycolysis, is transported into mitochondria to fuel the tricarboxylic acid (TCA) cycle, driving oxidative phosphorylation (OXPHOS) and ATP synthesis. The Mitochondrial Pyruvate Carrier (MPC) is crucial for this process, enabling the transport of pyruvate from the cytosol into the mitochondrial matrix. Due to its essential role, MPC dysfunction is associated with a range of diseases. In cancer, MPC disruption promotes the Warburg Effect, which favors aerobic glycolysis, and in turn encourages tumor growth, metastasis, and poor prognosis. Conversely, inhibiting MPC in the liver and muscle has shown therapeutic potential for type 2 diabetes (T2D) by enhancing glucose uptake, promoting fat oxidation, improving insulin sensitivity, and reducing gluconeogenesis. Additionally, neurodegenerative diseases often involve metabolic dysfunction linked to impaired mitochondrial energy metabolism, highlighting the therapeutic potential of targeting MPC to address these conditions. In humans, MPC is encoded by three homologous genes—MPC1, MPC1-like (MPC1L), and MPC2—and belongs to the recently identified triple-helix-bundle (THB) transporter family. MPC functions as a heterodimer, either MPC1–MPC2 or MPC1L–MPC2, with each protomer containing three transmembrane helices. Our long-term goal is to elucidate the transport mechanisms of MPC proteins and to develop targeted therapies for related diseases. In our preliminary studies, we engineered the human MPC1-2 complex (~25 kDa) and obtained a functional construct (~80 kDa) suitable for structural determination by cryogenic electron microscopy (cryo-EM). We resolved the structures of human MPC1–2 complex in the intermembrane space (IMS)-open and inhibitor-bound matrix-open states. Based on these findings, the objective of this proposal is to uncover the mechanisms underlying pyruvate transport, inhibition, and regulation of human MPC, and to develop its inhibitors for therapeutic purposes. Our projects aim to 1) Uncover the mechanism of pyruvate transport mediated by human MPC1-2 complex; 2) Elucidate the inhibitory mechanisms of existing inhibitors and develop novel modulators for human MPC1-2; 3) Extend the established approaches to investigate human MPC1L1 and MPC proteins in other species. Successful completion of this research will provide critical insights into pyruvate transport, a process fundamental to cellular metabolism, and establish a foundation for therapeutic strategies targeting MPC in diseases such as neurodegenerative disorders, cancer, and diabetes.
