A MAM-targeting therapeutic peptide restores autophagy homeostasis and ameliorates atherosclerosis

Mitochondria-associated ER membranes (MAMs) are critical hubs for Ca²⁺ signaling, energy homeostasis, and autophagy. Their dysregulation contributes to lipid-driven cardiovascular diseases; however, selective and reversible strategies to modulate MAM-associated protein-protein interactions (PPIs) remain limited. This study aimed to develop a targeted peptide to disrupt the IP₃R-GRP75-VDAC1 complex and evaluate its therapeutic efficacy in atherosclerosis.

Based on structural and interface analyses of the IP₃R-GRP75 complex, we designed cell-permeable MAM-targeting peptides. The activity of the lead candidate, Peptide 4, was assessed using proximity ligation assays, microscale thermophoresis (MST) analysis, cellular thermal shift assays, co-immunoprecipitation, live-cell Ca²⁺ imaging, and autophagy flux analyses in endothelial cells and macrophages under basal and oxidized low-density lipoprotein (oxLDL)-induced stress. The therapeutic efficacy was further evaluated in Western diet-fed ApoE^-/- mice.

Peptide 4 bound to GRP75, disrupted the IP₃R-GRP75 interaction, and selectively attenuated ER-to-mitochondria Ca²⁺ transfer. This controlled Ca²⁺ modulation modestly reduced cellular ATP levels, activated the AMPK-TFEB axis, and restored functional autophagic flux. These effects were preserved under oxLDL-induced lipid stress. Restoration of MAM architecture closely correlated with autophagy recovery and lipid clearance, indicating its potential utility as a pharmacodynamic indicator. In vivo, systemic administration of Peptide 4 significantly improved serum lipid profiles, attenuated aortic plaque formation, reduced cardiac lipid deposition, and normalized MAM architecture in ApoE^-/- mice.

Our findings identify peptide-mediated targeting of the IP₃R-GRP75 interaction as a promising strategy to modulate MAM structure, activate adaptive autophagy, and alleviate atherosclerotic pathology. This study supports organelle contact site modulation as both a therapeutic mechanism and a measurable disease-responsive feature, highlighting peptide-based modulation of protein-protein interactions as a promising approach for metabolic and cardiovascular diseases.