Vear, a Novel Golgi-associated Protein with VHS and γ-Adaptin “Ear” Domains

Poussu, Anssi; Lohi, Olli; Lehto, Veli‐Pekka

doi:10.1074/jbc.275.10.7176

Cited by 93 publications

(72 citation statements)

References 40 publications

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“…Three GGAs have been identified in humans (GGA1, GGA2, and GGA3). These proteins have modular structures consisting of an N-terminal VHS (VPS-27, Hrs, and STAM) domain followed by a GAT (GGA and TOM1) domain, a connecting hinge segment, and a C-terminal GAE domain, which has homology to the ear domain of ␥-adaptin (1)(2)(3)(4)(5). The VHS and GAT domains are highly conserved among the three mammalian GGAs with 60-75% identity across the N-terminal 300 aa (4).…”

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confidence: 99%

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Autoinhibition of the ligand-binding site of GGA1/3 VHS domains by an internal acidic cluster-dileucine motif

Doray

Bruns²,

Ghosh³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

111

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The GGAs (Golgi-localizing, ␥-adaptin ear homology domain, ARFbinding proteins) are a family of proteins implicated in protein trafficking from the Golgi to endosomes͞lysosomes. These proteins have modular structures with an N-terminal VHS (VPS-27, Hrs, and STAM) domain followed by a GAT (GGA and TOM1) domain, a connecting hinge segment, and a C-terminal GAE (␥-adaptin ear) domain. Isolated VHS domains have been shown to bind specifically to acidic cluster (AC)-dileucine motifs present in the cytoplasmic tails of the mannose 6-phosphate receptors. Here we report that full-length cytoplasmic GGA1 and GGA3 but not GGA2 bind the cation-independent mannose 6-phosphate receptor very poorly because of autoinhibition. This inhibition is caused by the binding of an AC-LL sequence present in the hinge segment to the ligand-binding site in the VHS domain. The inhibition depends on the phosphorylation of a serine located three residues upstream of the AC-LL motif. The serine is phosphorylated by casein kinase 2 in in vitro assays. Substitution of the GGA1 inhibitory sequence into the analogous location in GGA2, which lacks the AC-LL motif, results in autoinhibition of the latter protein. These data indicate that the activity of GGA1 and GGA3 is regulated by cycles of phosphorylation͞dephosphorylation.

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confidence: 99%

“…T he GGAs (Golgi-localizing, ␥-adaptin ear homology domain, ARF-binding proteins) are a recently described family of proteins involved in trafficking between the Golgi and endosomes (1)(2)(3)(4)(5). Three GGAs have been identified in humans (GGA1, GGA2, and GGA3).…”

mentioning

confidence: 99%

Autoinhibition of the ligand-binding site of GGA1/3 VHS domains by an internal acidic cluster-dileucine motif

Doray

Bruns²,

Ghosh³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

111

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“…Srcasm is a 52.7-kDa molecule that contains motifs consistent with a substrate for SFKs (23). Srcasm contains an amino-terminal VHS membrane binding domain (24), and motifs predicted to interact with the SH2 and SH3 domains of SFKs, and the SH2 domains of Grb2, and p85 PI3K (3,5). In addition, Srcasm can serve as a Fyn substrate and activate Fyn kinase activity.…”

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confidence: 99%

'Srcasm: a Novel SrcActivating and SignalingMolecule

Seykora¹,

Mei²,

Dotto³

et al. 2002

Journal of Biological Chemistry

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The Src family tyrosine kinase, Fyn, can facilitate regulation of cell proliferation and differentiation. Mice with mutations in the fyn gene have defects in the brain, immune system, and epidermal differentiation. To identify molecules that may interact with Fyn in the epidermis, we performed a yeast two-hybrid interaction screen of a murine keratinocyte library. A novel adaptor-like molecule was isolated and termed Srcasm for Src activating and signaling molecule. Murine Srcasm is a 52.7-kDa protein that contains a VHS membrane association domain and a number of tyrosine motifs suggesting that it may be a substrate for Src family kinases and serve as an adaptor protein. Northern blot analysis of murine tissues demonstrates that Srcasm expression is highest in brain and kidney. In situ hybridization analysis reveals that srcasm mRNA is expressed in regions of the epidermis and hair follicle where keratinocyte differentiation occurs. In the brain, srcasm mRNA distribution correlates with that of fyn, with both being highly expressed in the hippocampal and cerebellar Purkinje neurons. Fyn can phosphorylate Srcasm, and association of these molecules relies on cooperative binding between the SH2 and SH3 domains of Fyn and corresponding canonical binding sites in Srcasm. Srcasm is capable of interacting with Grb2 and the regulatory subunit of phosphoinositide 3-kinase, p85, in a phosphorylation-dependent manner. The evidence suggests that Srcasm may help promote Src family kinase signaling in cells.The Src family kinases (SFKs) 1 comprise nine highly similar tyrosine kinases that regulate a variety of cellular responses including proliferation, migration, differentiation, and survival (1). The SFKs share a common domain structure differing primarily in the amino-terminal 60 -80 amino acids (1, 2). There are several functional motifs common to all Src kinases: (i) the Src homology 2 (SH2) domain, which binds phosphotyrosine, preferentially within the context of acidic amino acids (3); (ii) the Src homology 3 (SH3) domain, which binds polyproline motifs (4 -6); (iii) the amino-terminal region Src homology 4 domain, which contains consensus sequences for myristoylation and/or palmitoylation (7); (iv) the carboxyl-terminal Src homology 1 domain, which contains the catalytic region and has a short carboxyl-terminal tail containing the major regulatory tyrosine (1, 2). Phosphorylation of the carboxyl-terminal regulatory tyrosine leads to an intramolecular association between the phosphotyrosine residue and the SH2 domain; this interaction decreases substrate access to the active site, thereby inhibiting kinase activity (8 -11). When the association of the carboxyl-terminal tyrosine with the SH2 domain is disrupted, kinase activity is increased (1, 2).Insights into the functional roles of SFKs can be gleaned from the limited yet distinct phenotype(s) of mice deficient for a specific kinase. For example, mice lacking Src exhibit defects in bone remodeling leading to osteopetrosis, and src Ϫ/Ϫ endothelial cells demonstrate d...

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“…In addition, a role for these proteins in the sorting into MVBs has also been suggested. GGA proteins are monomeric adaptors that are recruited to the TGN by the Arf-1 GTPase (22)(23)(24)(25) and mediate the transport of lysosomal enzymes. They consist of four distinct segments as follows: a VHS domain that binds an acidic di-leucine sorting signal found in the mannose 6-phosphate receptor and other proteins known to cycle between TGN and endosomes (26,27); a GAT (GGA and Tom) domain that interacts with the GTPbound form of Arf (22)(23)28); a hinge region that recruits clathrin (27,28); and a similar to the ␥-adaptin ear domain that exhibits sequence similarity to the ear region of ␥-adaptin and recruits a number of accessory proteins (24, 29 -31).…”

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confidence: 99%

Interactions of TOM1L1 with the Multivesicular Body Sorting Machinery

Puertollano

2005

Journal of Biological Chemistry

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Tom1L1 (Tom1-like1) and related proteins Tom1 (Target of Myb1) and Tom1L2 (Tom1-like2) constitute a new protein family characterized by the presence of a VHS (Vps27p/Hrs/Stam) domain in the N-terminal portion followed by a GAT (GGA and Tom) domain. Recently it was demonstrated that the GAT domain of both Tom1 and Tom1L1 binds ubiquitin, suggesting that these proteins might participate in the sorting of ubiquitinated proteins into multivesicular bodies (MVBs). Here we report a novel interaction between Tom1L1 and members of the MVB sorting machinery. Specifically, we found that the VHS domain of Tom1L1 interacts with Hrs (Hepatocyte growth factor-regulated tyrosine kinase substrate), whereas a PTAP motif, located between the VHS and GAT domain of Tom1L1, is responsible for binding to TSG101 (tumor susceptibility gene 101). Myc epitopetagged Tom1L1 showed a cytosolic distribution but was recruited to endosomes following Hrs expression. In addition, Tom1L1 possesses several tyrosine motifs at the C-terminal region that mediate interactions with members of the Src family kinases and other signaling proteins such as Grb2 and p85. We showed that a fraction of Fyn kinase localizes at endosomes and that this distribution becomes more evident after epidermal growth factor internalization. Moreover, expression of a constitutive active form of Fyn also promoted the recruitment of Tom1L1 to enlarged endosomes. Taken together, we propose that Tom1L1 could act as an intermediary between signaling and degradative pathways.Regulated degradation of cell surface proteins, particularly receptors involved in signaling pathways, is essential for the control of many biological processes, including cell proliferation, survival, migration, and differentiation (1, 2). Internalized membrane-protein cargo can be delivered either to recycling vesicles for transport back to the cell surface or to late endosomes for transfer to lysosomes and degradation. Multivesicular bodies (MVBs) 1 are the compartments where this sorting event takes place (3). Thus, proteins to be degraded are included into small vesicles that invaginate into the lumen of the endosome. Subsequent fusion of MVBs with lysosomes releases these vesicles into the lysosome lumen, where they are degraded by lysosomal hydrolases. In contrast, proteins that remain in the limiting membrane of MVBs are recycled to the trans-Golgi network (TGN) or plasma membrane. In the last few years, a number of genetic and biochemical studies have allowed the characterization of the molecular machinery implicated in the formation of MVBs. Hrs appears to be the first protein to be recruited to endosomes (4 -6) through an interaction of its FIVE domain with phosphatidylinositol 3-phosphate (7), a lipid highly enriched in endosomal membranes (8). This is followed by the consecutive recruitment of three multisubunit complexes termed ESCRT-I (9), ESCRT-II (10), and ESCRT-III (11). Finally, the AAA-type ATPase Vps4 binds ESCRT-III and, following MVB vesicle formation, promotes the dissociation of the E...

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Vear, a Novel Golgi-associated Protein with VHS and γ-Adaptin “Ear” Domains

Cited by 93 publications

References 40 publications

Autoinhibition of the ligand-binding site of GGA1/3 VHS domains by an internal acidic cluster-dileucine motif

Autoinhibition of the ligand-binding site of GGA1/3 VHS domains by an internal acidic cluster-dileucine motif

'Srcasm: a Novel SrcActivating and SignalingMolecule

Interactions of TOM1L1 with the Multivesicular Body Sorting Machinery

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