Interactions between adaptor protein-1 of the clathrin coat and microtubules via type 1a microtubule-associated proteins.
The classical view suggests that adaptor proteins of the clathrin coat mediate the sorting of cargo protein passengers into clathrin-coated pits and the recruitment of clathrin into budding areas in the donor membrane. In the present study, we provide biochemical and morphological evidence that the adaptor protein 1 (AP-1) adaptor of the trans-Golgi network clathrin interacts with microtubules. AP-1 in cytosolic extracts interacted with in vitro assembled microtubules, and these interactions were inhibited by ATP depletion of the extracts or in the presence of 5'-adenylylimidodiphosphate. An overexpressed gamma-subunit of the AP-1 complex associated with microtubules, suggesting that this subunit may mediate the interaction of AP-1 with the cytoskeleton. Purified AP-1 did not interact with purified microtubules, but interaction occurred when an isolated microtubule-associated protein fraction was added to the reaction mix. The gamma-adaptin subunit of AP-1 specifically co-immunoprecipitated with a microtubule-associated protein of type 1a from rat brain cytosol. This suggests that type 1a microtubule-associated protein may mediate the association of AP-1 with microtubules in the cytoplasm. The microtubule binding activity of AP-1 was markedly inhibited in cytosol of mitotic cells. By means of its interaction with microtubule-associated proteins, we propose novel roles for AP-1 adaptors in modulating the dynamics of the cytoskeleton, the stability and shape of coated organelles, and the loading of nascent AP-1-coated vesicles onto appropriate microtubular tracks.
Orzech
E
E
Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Livshits
L
L
Leyt
J
J
Okhrimenko
H
H
Reich
V
V
Cohen
S
S
Weiss
A
A
Melamed-Book
N
N
Lebendiker
M
M
Altschuler
Y
Y
Aroeti
B
B
D033982:Adaptor Protein Complex gamma Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry*; D002460:Cell Line; D004285:Dogs; D008565:Membrane Proteins / Q000737:chemistry*; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000737:chemistry*; D008870:Microtubules / Q000737:chemistry*; D011233:Precipitin Tests; D014404:Tubulin / Q000737:chemistry
D033982:Adaptor Protein Complex gamma Subunits; D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; C490546:Map1a protein, rat; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D014404:Tubulin