Interactions between Adaptor Protein-1 of the Clathrin Coat and Microtubules via Type 1a Microtubule-associated Proteins

Abstract

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 ␥-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 ␥-adaptin subunit of AP-1 specifically co-immunoprecipitated with a microtubuleassociated 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.

The AP-1 clathrin adaptor facilitates cilium formation and functions with RAB-8 in C. elegans ciliary membrane transport

“…Consistent with this notion, AP-1 interacts with microtubules and coimmunoprecipitates with microtubule-associated proteins (Orzech et al, 2001). Furthermore, ciliary microtubule acetylation defects are found in mammalian cells overexpressing Rab8(wt) or Rab8-GTP (Nachury et al, 2007), which is relevant to AP-1 based on our findings (discussed below) that AP-1 and RAB-8 function in a common ciliary membrane transport pathway in C. elegans.…”

Effect of methylene blue on the genomic response to reperfusion injury induced by cardiac arrest and cardiopulmonary resuscitation in porcine brain

“…Our observations suggested that vesicle trafficking might be affected by MB since proteins which mediate transport between ER and Golgi such as SEC22b, STX5, KDELR2 and ERGIC1 [75,76,78] and VPS16 and GGA3 between Golgi and the endosomes [79,80] were up-regulated. On the other hand, proteins such as: VAMP3, a vesicle-associated membrane protein involved in regulating membrane traffic; AP1S2, modulating the dynamics of the cytoskeleton [81]; and GOSR2 involved in transport of proteins from the cis/medial-Golgi to the trans-Golgi network [75]; were down-regulated by MB.…”

Presenilin-Based Genetic Screens in Drosophila melanogaster Identify Novel Notch Pathway Modifiers

“…There are at least four distinct adaptor protein (AP) complexes that link clathrin to membranes, coordinate clathrin coat assembly, and recruit cargo proteins. AP-1 functions in multiple steps in vesicle trafficking and cargo sorting from the Golgi to endosomes and the plasma membrane and is critical for the sorting and recycling of receptors to correct plasma membrane domains (Futter et al 1998;Nakagawa et al 2000;Orzech et al 2001;Gan et al 2002;Pagano et al 2004). The m-chain of AP-1 appears to be responsible for sorting cargo proteins into developing vesicles.…”