adapterprotein

An adapter protein, or docking protein, is a non-enzymatic molecule that links components of a signaling pathway. By presenting binding surfaces for multiple partners, adapters assemble multi-protein complexes that control where, when, and how signals are transmitted. They typically do not catalyze chemical reactions; instead they facilitate interactions and coordinate signaling throughput.

Adapters use modular interaction domains to recognize specific motifs. Common domains include SH2 and SH3, which bind phosphotyrosine residues and proline-rich sequences, respectively, as well as PH, PTB, PDZ, and WW domains. The arrangement of these domains determines binding partners, subcellular localization, and the signaling outcome.

Examples include Grb2, Crk, and Shc family proteins that connect activated receptor tyrosine kinases to Ras signaling by recruiting SOS or other effectors. LAT and SLP-76 act as transmembrane and cytoplasmic adaptors in T cell receptor signaling. 14-3-3 proteins function as ubiquitous adaptors that regulate diverse networks by binding phosphoserine/phosphothreonine motifs. The AP-2 adaptor complex participates in clathrin-mediated endocytosis by linking cargo to the clathrin coat.

Role and regulation: By controlling which components are brought together and where, adapter proteins shape the strength and duration of signaling. Their interactions can be regulated by phosphorylation, conformational changes, and changes in expression or localization.

Clinical relevance: Alterations in adaptor proteins have been linked to cancer, immunodeficiencies, and developmental disorders, underscoring their essential role in cellular communication.