Abstract

The AP (adaptor protein) complexes are heterotetrameric protein complexes that mediate intracellular membrane trafficking along endocytic and secretory transport pathways. There are five different AP complexes: AP-1, AP-2 and AP-3 are clathrin-associated complexes; whereas AP-4 and AP-5 are not. These five AP complexes localize to different intracellular compartments and mediate membrane trafficking in distinct pathways. They recognize and concentrate cargo proteins into vesicular carriers that mediate transport from a donor membrane to a target organellar membrane. AP complexes play important roles in maintaining the normal physiological function of eukaryotic cells. Dysfunction of AP complexes has been implicated in a variety of inherited disorders, including: MEDNIK (mental retardation, enteropathy, deafness, peripheral neuropathy, ichthyosis and keratodermia) syndrome, Fried syndrome, HPS (Hermansky–Pudlak syndrome) and HSP (hereditary spastic paraplegia).

Highlights

  • In the endocytic and secretory pathways, cargo proteins destined for transport to distinct locations are collectively assembled into vesicles and delivered to their target sites by vesicular trafficking

  • Five adaptor protein (AP) complexes have been identified to date: AP-1, AP-2, AP-3, AP-4 and AP-5, each composed by two large subunits, one medium-sized subunit (μ1–5) and one small-sized subunit (σ 1–5) (Figure 2A)

  • We further showed that the membrane recruitment of both AP-1A and AP-1B is sensitive to the Arf–GEF inhibitor brefeldin A (BFA)

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Summary

Adaptor protein complexes and intracellular transport

Synopsis The AP (adaptor protein) complexes are heterotetrameric protein complexes that mediate intracellular membrane trafficking along endocytic and secretory transport pathways. There are five different AP complexes: AP-1, AP-2 and AP-3 are clathrin-associated complexes; whereas AP-4 and AP-5 are not. These five AP complexes localize to different intracellular compartments and mediate membrane trafficking in distinct pathways. They recognize and concentrate cargo proteins into vesicular carriers that mediate transport from a donor membrane to a target organellar membrane. AP complexes play important roles in maintaining the normal physiological function of eukaryotic cells. (2014) Adaptor protein complexes and intracellular transport.

INTRODUCTION
AP complexes and protein transport
LRO biogenesis
SORTING SIGNALS RECOGNIZED BY AP COMPLEXES
STRUCTURAL ASPECTS OF CARGO BINDING OF AP COMPLEXES
PHYSIOLOGICAL ROLES OF THE AP COMPLEXES
CONCLUSIONS AND PERSPECTIVES
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