CD36 phosphorylation alters the thrombospondin binding site and reduces internal cavity accessibility and volume

CD36 is a membrane protein with diverse roles in health and disease, and its function can be modulated through phosphorylation. Research has shown that phosphorylation of Thr92 reduces CD36's affinity for thrombospondin-1 (TSP-1), a protein that triggers antiangiogenic signaling. Conversely, phosphorylation of Ser237 hampers CD36's ability to absorb fatty acids, which has implications for energy metabolism.

However, the crystal structure of CD36 lacks phosphorylation, leaving unclear how the protein's function is regulated by phosphorylation. This study offers an atomically detailed computational analysis of CD36 in both unphosphorylated and dual phosphorylated states, using molecular dynamics simulations over 30 microseconds and Markov state models.

For the first time, the research team discovered a hidden pocket on CD36's surface formed by phosphorylation. This pocket, along with a loop spanning residues 121-131, creates a high affinity binding site for TSP-1-derived ligands. The binding site shifts away from the standard location, which could explain the disruption of antiangiogenic signaling when CD36 is phosphorylated.

The data also suggests that phosphorylation increases helicity and compaction within the helix-loop region between residues 296-331, narrowing one of the internal cavity's entrances and reducing its overall volume. This conformational change could provide a mechanism for the decrease in fatty acid uptake seen when CD36 is phosphorylated.

The findings offer structural insights that could help design CD36 modulators and highlight the importance of targeting phosphorylation-induced CD36 conformations in diseases characterized by angiogenesis or metabolic dysfunction.