Abstract
Many plasma membrane proteins destined for endocytosis are concentrated into clathrin-coated pits through the recognition of a tyrosine-based motif in their cytosolic domains by an adaptor (AP-2) complex. The mu2 subunit of isolated AP-2 complexes binds specifically, but rather weakly, to proteins bearing the tyrosine-based signal. We now demonstrate, using peptides with a photoreactive probe, that this binding is strengthened significantly when the AP-2 complex is present in clathrin coats, indicating that there is cooperativity between receptor-AP-2 interactions and coat formation. Phosphoinositides with a phosphate at the D-3 position of the inositol ring, but not other isomers, also increase the affinity of the AP-2 complex for the tyrosine-based motif. AP-2 is the first protein known (in any context) to interact with phosphatidylinositol 3-phosphate. Our findings indicate that receptor recruitment can be coupled to clathrin coat assembly and suggest a mechanism for regulation of membrane traffic by lipid products of phosphoinositide 3-kinases.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Protein Complex 1*
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Adaptor Protein Complex 2*
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Adaptor Protein Complex 3*
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Adaptor Protein Complex mu Subunits*
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Adaptor Proteins, Vesicular Transport
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Alanine / metabolism
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Amino Acid Sequence
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Animals
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Binding Sites
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Cattle
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Clathrin / metabolism*
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Endocytosis*
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Glycoproteins*
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Membrane Glycoproteins / metabolism
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Membrane Proteins*
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Models, Molecular
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Molecular Sequence Data
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Nerve Tissue Proteins / metabolism*
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Phosphatidylinositols / metabolism
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Phosphoproteins / metabolism*
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Protein Conformation
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Protein Sorting Signals / metabolism*
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Tyrosine / metabolism
Substances
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AP3M2 protein, human
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Adaptor Protein Complex 1
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Adaptor Protein Complex 2
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Adaptor Protein Complex 3
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Adaptor Protein Complex mu Subunits
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Adaptor Proteins, Vesicular Transport
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Clathrin
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Glycoproteins
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Membrane Glycoproteins
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Membrane Proteins
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Nerve Tissue Proteins
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Phosphatidylinositols
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Phosphoproteins
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Protein Sorting Signals
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adaptor protein complex 1, mu 2 subunit
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adaptor protein complex 2, mu 2 subunit
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Tyrosine
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Alanine