A Novel AP-2 Adaptor Interaction Motif Initially Identified in the Long-splice Isoform of Synaptojanin 1, SJ170

Section: Methodsmentioning

confidence: 99%

α-AP-2 Directs Myosin VI-dependent Endocytosis of Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channels in the Intestine

Collaco

Jakab

Hegan

et al. 2010

“…21 and Fig. 2C): the DLL clathrin-binding motif (43), two DPF ␣-adaptin-interaction motifs (44) and the NPF, EH-(45) or AP2-binding motif (46). AAK1 could thus act as an adaptor protein for the recruitment of different endocytic partners to the Notch complex.…”

Section: Aak1 Interacts With the Activated Membrane-anchoredmentioning

confidence: 99%

The Adaptor-associated Kinase 1, AAK1, Is a Positive Regulator of the Notch Pathway

Gupta-Rossi

Ortica

Meas-Yedid

et al. 2011

The Notch pathway is involved in cell-cell signaling during development and adulthood from invertebrates to higher eukaryotes. Activation of the Notch receptor by its ligands relies upon a multi-step processing. The extracellular part of the receptor is removed by a metalloprotease of the ADAM family and the remaining fragment is cleaved within its transmembrane domain by a presenilin-dependent ␥-secretase activity. ␥-Secretase processing of Notch has been shown to depend upon monoubiquitination as well as clathrin-mediated endocytosis (CME). We show here that AAK1, the adaptor-associated kinase 1, directly interacts with the membrane-tethered active form of Notch released by metalloprotease cleavage. Active AAK1 acts upstream of the ␥-secretase cleavage by stabilizing both the membrane-tethered activated form of Notch and its monoubiquitinated counterpart. We propose that AAK1 acts as an adaptor for Notch interaction with components of the clathrin-mediated pathway such as Eps15b. Moreover, transfected AAK1 increases the localization of activated Notch to Rab5-positive endocytic vesicles, while AAK1 depletion or overexpression of Numb, an inhibitor of the pathway, interferes with this localization. These results suggest that after ligand-induced activation of Notch, the membrane-tethered form can be directed to different endocytic pathways leading to distinct fates.The Notch gene encodes a receptor, matured by furin, and present at the cell surface as an heterodimer (1, 2). Notch activation is induced upon ligand binding and leads to its extracellular cleavage by TNF-␣-converting enzyme (TACE) 2 (3, 4), followed by a second cleavage within the transmembrane domain by a ␥-secretase complex. The released intracellular domain of Notch translocates to the nucleus and induces transcription of target genes together with the CSL and Mastermind cofactors. Ligand-induced activation of Notch is strictly regulated at several levels, both at the extracellular and the intracellular levels (5-7).An increasing number of data reveals that the activity of both Notch receptor and its ligands is regulated by internalization as well as ubiquitination events (8,9). A large repertoire of Notch pathway regulators has been identified, mainly in invertebrates, and conflicting data have emerged regarding Notch activity and trafficking (5). On one hand, endocytosis appears important for Notch activation in the signal-receiving cell (10 -13) while other studies point to an inhibitory effect (14 -18). Our data suggest that, in mammalian cells, both monoubiquitination and endocytosis are required before ␥-secretase cleavage of ligandactivated Notch (10).As the Notch pathway is conserved throughout evolution, we scanned the literature for genetic modulators of the pathway in invertebrates to further understand the intracellular events that control Notch activation. Loss of worm sel-5 (SEL for suppressor/enhancer of Lin12) results in suppression of the constitutive activity of lin-12(d) (equivalent to the metalloprotease-cleaved Notch or ⌬E c...

“…Accessory proteins interact with the ␣ and ␤2 ear domains via short peptide sequences or structural motifs that bind to sites on either the sandwich or platform subdomains. For instance, DPW (11) (12,13,14) (where X is any amino acid) (motifs denoted in PROSITE syntax) bind to the ␣-ear sandwich, while DP[FW] (7,11) and FXDXF motifs (11,14) bind to the ␣-ear platform, all in an extended conformation. On the other hand, a helical [DE] n X 1-2 FXX[FL]XXXR motif (15,9,10) and probably the extended DP[FW] motif as well (8) bind to the ␤2-ear platform.…”

mentioning

confidence: 99%

Bivalent Motif-Ear Interactions Mediate the Association of the Accessory Protein Tepsin with the AP-4 Adaptor Complex

Mattera

Guardia

Sidhu

et al. 2015

The heterotetrameric (⑀-␤4-4-4) complex adaptor protein 4 (AP-4) is a component of a non-clathrin coat involved in protein sorting at the trans-Golgi network (TGN). Considerable interest in this complex has arisen from the recent discovery that mutations in each of its four subunits are the cause of a congenital intellectual disability and movement disorder in humans. Despite its physiological importance, the structure and function of this coat remain poorly understood. To investigate the assembly of the AP-4 coat, we dissected the determinants of interaction of AP-4 with its only known accessory protein, the ENTH/VHS-domain-containing protein tepsin. Using a variety of protein interaction assays, we found that tepsin comprises two phylogenetically conserved peptide motifs, Shuttling of cargo between membrane-bound compartments of the endomembrane system of eukaryotic cells is carried out by transport vesicles that bud from a donor compartment and fuse with an acceptor compartment (1). Cargo selection and vesicle budding are both mediated by protein coats that assemble on the cytosolic aspect of the donor compartment from components recruited from the cytosol. To date, about ten different protein coats have been described that participate in vesicular transport at various stages of the endomembrane system. Most of them consist of an outer "scaffold" layer and an inner "adaptor" layer, although in some cases both layers are tightly intertwined. Among the best-characterized protein coats are those containing clathrin as a scaffold and the AP-1 2 and AP-2 complexes as adaptors (2, 3, 4, 5). AP-1 and AP-2 are heterotetramers composed of homologous ␥-␤1-1-1 and ␣-␤2-2-2 subunits, respectively (Fig. 1A). The large ␥ and ␤1 subunits of AP-1, and ␣ and ␤2 subunits of AP-2, have a modular organization consisting of a folded N-terminal "trunk" domain, a largely unstructured "hinge" segment, and a folded C-terminal "ear" or "appendage" domain. The trunk domains of the large subunits, plus the whole and subunits, constitute a "core" that mediates membrane recruitment through interaction with specific phosphoinositides and/or Arf-family GTPases, as well as cargo selection through recognition of sorting signals in the cytosolic tails of transmembrane proteins. The hinge segments extend from the core and interact with the clathrin scaffold via LLDLD-type "clathrin-box" motifs (6). Finally, the ear domains interact with a variety of accessory proteins, some of which regulate coat assembly and interactions with the cytoskeleton, while others function as additional adaptors.X-ray crystallographic analyses of the ␣-and ␤2-ear domains of AP-2 revealed that they have a similar bilobed structure comprising an N-terminal immunoglobulin-like ␤-sandwich subdomain and a C-terminal platform subdomain (7,8,9,10) (Fig. 1A). Accessory proteins interact with the ␣ and ␤2 ear domains via short peptide sequences or structural motifs that bind to sites on either the sandwich or platform subdomains. For instance, DPW (11) and WXX[FW]X[DE] motifs...