Targeting Monocarboxylate Transporters to Overcome Metabolic Plasticity in Melanoma

Rationale: Monocarboxylate transporters MCT1 and MCT4 play a central role in tumor metabolic adaptation by regulating lactate export, contributing to tumor progression and resistance to therapy. However, the structural determinants underlying their functional differences and inhibitor sensitivity remain poorly understood, limiting the development of effective dual-targeting strategies. Methods: We conducted a structure-based investigation of MCT1 and MCT4 by integrating AI-based structure prediction, homology modeling, and all-atom molecular dynamics simulations. Complete models of each transporter were built in complex with the chaperone basigin-2 and embedded in a membrane environment. Inward- and outward-facing conformations were analyzed to compare substrate and inhibitor binding. Structural, electrostatic, and pKa analyses were performed to characterize transport mechanisms and isoform-specific differences. Results: Simulations identified a conserved Asp-Arg salt bridge as a key determinant of proton coupling and conformational transitions in both MCT1 and MCT4. Shared residues defining the substrate-binding site and transport pathway were observed across isoforms. Notably, isoform-specific differences in local electrostatics and residue pKa values emerged, providing a mechanistic explanation for their differential sensitivity to competitive inhibitors. Additionally, a putative acriflavine binding site was structurally characterized, revealing interaction features consistent with its role in disrupting MCT::basigin-2 complex formation. Conclusions: This study links conserved structural features of MCT transporters with isoform-specific electrostatics and dynamics that govern substrate transport and inhibitor sensitivity. These findings provide a structural framework to guide the rational design of both competitive and non-competitive inhibitors targeting MCT1 and MCT4, supporting the development of dual-targeting strategies to overcome metabolic plasticity and therapeutic resistance in melanoma. Disclosure of Interest: None declared