Membrane Protein Clustering as a Key Determinant of Endocytosis: Natural Mechanisms, Nonintentional Transporter Internalization, and Engineered Multivalent Nanocarriers

Membrane protein clustering frequently precedes endocytosis, but its functional role differs across protein classes. Here, a multivalency-aware framework is proposed, in which clustering acts as a thresholding mechanism that governs internalization and postentry fate. For receptors, clustering operates as an intentional signaling strategy that recruits endocytic machinery and controls trafficking routes. In contrast, transporter clustering more often reflects quality-control or crowding-driven processes, leading to context-dependent internalization and degradation. Quantitative studies define practical limits, such as optimal cluster sizes and superselective responses near critical receptor densities. Extracellular multivalency, including lectin-glycolipid lattices, can also generate membrane curvature and drive clathrin-independent uptake. These principles unify natural and engineered systems, explaining how multivalent nanoparticles, antibody-drug conjugates, and targeted degraders exploit clustering to achieve selective delivery. This perspective highlights threshold-aware design and postentry fate programming as key strategies for improving efficacy and safety in drug delivery and degradation technologies.