Beyond Canonical GPCR Desensitization: Integrating Arrestin Deubiquitination into a Two-Level Model

G protein-coupled receptors (GPCRs) form the largest family of cell-surface signaling proteins and remain the most exploited drug targets. Their regulation depends on desensitization, the attenuation of receptor responsiveness following sustained or repeated stimulation. The canonical framework, validated for rhodopsin and the β2-adrenergic receptor, describes desensitization as GRK-mediated receptor phosphorylation, arrestin recruitment, and steric occlusion of G protein coupling. This receptor-centric view has been supported primarily by time-course assays of second messenger generation, which capture rapid, reversible attenuation at the plasma membrane. Recent studies, however, reveal a receptor-distal program in which arrestin deubiquitination, regulated by EGFR–Akt–USP33 signaling, converts arrestin into a Gβγ-sequestering state and drives nuclear redistribution of signaling components. This perspective has been advanced through washout–rechallenge assays (pulse‑chase‑pulse), which demonstrate diminished responsiveness upon repeated stimulation even after receptor recovery. Integrating these complementary approaches, we propose a two-level framework for GPCR desensitization. Level 1 (proximal) reflects rapid receptor-core uncoupling, suited to transient stimulation. Level 2 (distal) reflects slower, trafficking-dependent redistribution of signaling machinery, producing more durable attenuation. This layered model reconciles divergent experimental findings, explains receptor subtype diversity, and highlights how desensitization extends beyond receptor blockade to spatial reorganization of signaling components. By linking methodological differences to mechanistic insights, this framework provides a unified view of GPCR desensitization. It informs future directions in biased agonism, acute tolerance, and the design of therapeutics with tailored desensitization profiles.