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Results for “Adaptor Protein Complex 1”

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At least 19 recordsLinked to original sources

PubMed1999

Phylogenetic analysis of components of the eukaryotic vesicle transport system reveals a common origin of adaptor protein complexes 1, 2, and 3 and the F subcomplex of the coatomer COPI.

Eukaryotic vesicular transport requires the recognition of membranes through specific protein complexes. The heterotetrameric adaptor protein complexes 1, 2, and 3 (AP1/2/3) are composed of two large, one small, and one medium adaptin subunit. We isolated and characterized the cDNA for Arabidopsis gamma-adaptin and performed a phylogenetic analysis of all adaptin subunits (proteins) in the context of all known homologous proteins. This analysis revealed (i) that the large subunits of AP1/2/3 are homologous and (ii) two subunits of the heptameric coatomer I (COPI) complex belong to this gene family. In addition, all small subunits and the aminoterminal domain of the medium subunits of the heterotetramers are homologous to each other; this also holds for two corresponding subunits of the COPI complex. AP1/2/3 and a substructure (heterotetrameric, F-COPI subcomplex) of the heptameric COPI had a common ancestral complex (called pre-F-COPI). Since all large and all small/medium subunits share sequence similarity, the ancestor of this complex is inferred to have been a heterodimer composed of one large and one small subunit. The situation encountered today is the result of successive rounds of coordinated gene duplications of both the large and the small/medium subunits, with F-COPI being the first that separated from the ancestral pre-F-COPI.

Adaptor Protein Complex 1↗

PubMed2000

Interactions of HIV-1 nef with the mu subunits of adaptor protein complexes 1, 2, and 3: role of the dileucine-based sorting motif.

HIV-1 Nef interacts with cellular adaptor protein (AP) complexes and their medium (mu) subunits. However, the role of the dileucine-based sorting motif within Nef in these interactions has been incompletely characterized. Here, yeast two-hybrid assays indicated that HIV-1 Nef interacted not only with the mu subunits of AP-1 and AP-2, but also with that of AP-3. The interactions with mu1 and mu3 were markedly stronger than the interaction with mu2. Leucine residues of the sorting motif were required for the interactions with mu3 and mu2 and contributed to the interaction with mu1. Confocal immunofluorescence microscopy indicated that Nef, AP-1, and AP-3 (but not AP-2) were concentrated in a juxtanuclear region near the cell center, potentially facilitating interaction between Nef and the mu1 and mu3 subunits. However, leucine residues of the sorting motif were not required for this subcellular localization of Nef. These data suggest that the dileucine motif, required for optimal viral replication, functions through interactions with a variety of AP complexes, including AP-3, potentially by recruiting adaptor complexes to subcellular locations specified by additional determinants in the Nef protein.

Adaptor Protein Complex 1↗

PubMed2001

Herpes simplex virus gE/gI sorts nascent virions to epithelial cell junctions, promoting virus spread.

Alphaherpesviruses spread rapidly through dermal tissues and within synaptically connected neuronal circuitry. Spread of virus particles in epithelial tissues involves movement across cell junctions. Herpes simplex virus (HSV), varicella-zoster virus (VZV), and pseudorabies virus (PRV) all utilize a complex of two glycoproteins, gE and gI, to move from cell to cell. HSV gE/gI appears to function primarily, if not exclusively, in polarized cells such as epithelial cells and neurons and not in nonpolarized cells or cells that form less extensive cell junctions. Here, we show that HSV particles are specifically sorted to cell junctions and few virions reach the apical surfaces of polarized epithelial cells. gE/gI participates in this sorting. Mutant HSV virions lacking gE or just the cytoplasmic domain of gE were rarely found at cell junctions; instead, they were found on apical surfaces and in cell culture fluids and accumulated in the cytoplasm. A component of the AP-1 clathrin adapter complexes, mu1B, that is involved in sorting of proteins to basolateral surfaces was involved in targeting of PRV particles to lateral surfaces. These results are related to recent observations that (i) HSV gE/gI localizes specifically to the trans-Golgi network (TGN) during early phases of infection but moves out to cell junctions at intermediate to late times (T. McMillan and D. C. Johnson, J. Virol., in press) and (ii) PRV gE/gI participates in envelopment of nucleocapsids into cytoplasmic membrane vesicles (A. R. Brack, B. G. Klupp, H. Granzow, R. Tirabassi, L. W. Enquist, and T. C. Mettenleiter, J. Virol. 74:4004-4016, 2000). Therefore, interactions between the cytoplasmic domains of gE/gI and the AP-1 cellular sorting machinery cause glycoprotein accumulation and envelopment into specific TGN compartments that are sorted to lateral cell surfaces. Delivery of virus particles to cell junctions would be expected to enhance virus spread and enable viruses to avoid host immune defenses.

Adaptor Protein Complex 1↗

PubMed1999

Phosphorylation of the medium chain subunit of the AP-2 adaptor complex does not influence its interaction with the tyrosine based internalisation motif of TGN38.

Tyrosine based motifs conforming to the consensus YXXphi (where phi represents a bulky hydrophobic residue) have been shown to interact with the medium chain subunit of clathrin adaptor complexes. These medium chains are targets for phosphorylation by a kinase activity associated with clathrin coated vesicles. We have used the clathrin coated vesicle associated kinase activity to specifically phosphorylate a soluble recombinant fusion protein of mu2, the medium chain subunit of the plasma membrane associated adaptor protein complex AP-2. We have tested whether this phosphorylation has any effect on the interaction of mu2 with the tyrosine based motif containing protein, TGN38, that has previously been shown to interact with mu2. Phosphorylation of mu2 was shown to have no significant effect on the in vitro interaction of mu2 with the cytosolic domain of TGN38, indicating that reversible phosphorylation of mu2 does not play a role in regulating its direct interaction with tyrosine based internalisation motifs. In addition, although a casein kinase II-like activity has been shown to be associated with clathrin coated vesicles, we show that mu2 is not phosphorylated by casein kinase II implying that another kinase activity is present in clathrin coated vesicles. Furthermore the kinase activity associated with clathrin coated vesicles was shown to be capable of phosphorylating dynamin 1. Phosphorylation of dynamin 1 has previously been shown to regulate its interaction with other proteins involved in clathrin mediated endocytosis.

Adaptor Protein Complex 1↗

PubMed1994

Purification of Golgi adaptor protein 1 from bovine adrenal gland and characterization of its beta 1 (beta') subunit by microsequencing.

A method for the purification of the Golgi adaptor protein 1 from bovine adrenal gland tissue was devised to investigate the relationship of its beta 1 (formerly referred to as beta') subunit to known beta-type sequences. Adrenal gland tissue was chosen for this study because it yielded 2-3 times more adaptor protein 1 than a comparable preparation from bovine brain. Like its neuronal isoform, the beta 1 subunit from adrenal gland adaptor protein 1 is readily cleaved by trypsin into a 63-kDa N-terminal fragment and a 40-kDa C-terminal fragment, while the gamma subunit is largely refractory to digestion. Based on microsequencing of 167 residues from the 63-kDa fragment, we noted 11 differences to the corresponding region of the beta 2 (formerly beta) subunit of the plasma membrane adaptor protein 2, but only one difference to the corresponding region of a beta-type protein encoded by the rat cDNA clone AP105a which is supposed to be a variant of the beta 2 subunit of the plasma membrane adaptor protein 2 [Kirchhausen, T., Nathanson, K. L., Matsui, W., Vaisberg, A., Chow, E. P., Burne, C., Keen, J. H. & Davis, A. E. (1989) Proc. Natl Acad. Sci. USA 84, 8805-8809]. Alignment of 187 residues from the 40-kDa beta 1 C-terminal fragment revealed differences in 77 positions to the corresponding region of the beta 2 subunit and differences in 23 positions compared to the supposed beta 2-like protein. These findings suggest that the protein encoded by the rat cDNA clone AP105a is more closely related to the beta 1 subunit of the bovine adrenal Golgi adaptor protein 1 than to the beta 2 subunit of the rat plasma membrane adaptor protein 2.

Adaptor Protein Complex 1↗

PubMed1998

Interleukin-1.

Interleukin 1 (IL1) is a primary regulator of inflammatory and immune responses. Via its type I receptor it activates specific protein kinases, including the NF kappa B inducing kinase (NIK) and three distinct mitogen-activated protein (MAP) kinase cascades. These modulate a number of transcription factors including NF kappa B, AP1 and CREB each of which regulate a plethora of immediate early genes central to the inflammatory response. Phase I clinical trials of the soluble type I receptor and IRAP indicate that these have potential anti-inflammatory effects.

Adaptor Protein Complex 1↗

PubMed1999

Toxoplasma gondii resides in a vacuole that avoids fusion with host cell endocytic and exocytic vesicular trafficking pathways.

Toxoplasma gondii actively penetrates its vertebrate host cell to establish a nonfusigenic compartment called the parasitophorous vacuole (PV) that has previously been characterized primarily in phagocytic cells. To determine the fate of this unique compartment in nonphagocytic cells, we examined the trafficking of host cell proteins and lipids in Toxoplasma-infected fibroblasts using quantitative immunofluorescence and immunoelectron microscopy. Toxoplasma-containing vacuoles remained segregated from all levels of the endocytic pathway, as shown by the absence of delivery of transferrin receptors, mannose phosphate receptors, and the lysosomal-associated protein LAMP1 to the vacuole. The PV was also inaccessible to lipids (DiIC16, and GM1) that were internalized from the plasma membrane via the endocytic system. In contrast, vacuoles containing dead parasites or zymosan sequentially acquired both endosomal and lysosomal protein markers and host lipids, reflecting the competency of fibroblasts to process phagocytic vacuoles. The mature PV often lies adjacent to the host cell Golgi, suggesting that it may intersect with vesicles from the exocytic pathway. Despite this proximity, the PV was inaccessible to nitrobenzadiazole-labeled sphingolipids exported from the Golgi and did not contain the host protein markers AP1 or beta-COP. Our results demonstrate that Toxoplasma resides in a compartment that excludes delivery of protein and lipid components from the host cell endocytic and exocytic pathways.

3T3 Cells↗

PubMed1997

Functional domain mapping of the clathrin-associated adaptor medium chains mu1 and mu2.

The clathrin-associated adaptors AP-1 and AP-2 are heterotetrameric complexes involved in the recognition of sorting signals present within the cytosolic domain of integral membrane proteins. The medium chains of these complexes, mu1 and mu2, have been implicated in two types of interaction: assembly with the beta1 and beta2 chains of the corresponding complexes and recognition of tyrosine-based sorting signals. In this study, we report the results of a structure-function analysis of the mu1 and mu2 chains aimed at identifying regions of the molecules that are responsible for each of the two interactions. Analyses using the yeast two-hybrid system and proteolytic digestion experiments suggest that mu1 and mu2 have a bipartite structure, with the amino-terminal one-third (residues 1-145 of mu1 and mu2) being involved in assembly with the beta chains and the carboxyl-terminal two-thirds (residues 147-423 of mu1 and 164-435 of mu2) binding tyrosine-based sorting signals. These observations support a model in which the amino-terminal one-third of mu2 is embedded within the core of the AP-2 complex, while the carboxyl-terminal two-thirds of the protein are exposed to the medium, placing this region in a position to interact with tyrosine-based sorting signals.

Adaptor Protein Complex 1↗

PubMed1994

Cloning of Drosophila beta-adaptin and its localization on expression in mammalian cells.

A Drosophila cDNA (BAD1) encoding a structural and assembly-competent homologue of the mammalian coated pit beta-adaptins (beta and beta') has been cloned and sequenced. In its amino-terminal region (residues 1-575), the BAD1 sequence appears intermediate between that of the mammalian beta-adaptin and a predicted sequence, from cDNA 105a, which appears to code for a version of beta'-adaptin. To test its functional characteristics, a 'myc'-tagged version of BAD1 was expressed in Cos cells. The BAD1 protein was detected most clearly in plasma membrane coated pits, where it colocalized with alpha-adaptin, although other coated pits were noted which apparently did not contain alpha-adaptin. However, these are probably gamma-adaptin containing pits, as BAD1 was also found colocalized with gamma-adaptin in Golgi coated pits in which, typically, alpha-adaptin is absent. Immunoprecipitation experiments confirmed that the BAD1 protein was present in both types of adaptor complex, unlike beta-adaptin which complexes with alpha-adaptin and beta'-adaptin which partners gamma-adaptin exclusively. In spite of this, BAD1 expression does not appear to mix alpha-adaptin and gamma-adaptin distribution amongst all the coated pits: thus the location of these adaptor complexes in mammalian cells does not depend on the differences between beta subunits but rather on membrane-specific interactions of other adaptor polypeptides. The differential interaction of beta with alpha-adaptin and beta' with gamma-adaptin in mammalian cells is likely to depend on the few non-conservative differences between their respective sequences and BAD1. Four of these (one with respect to beta and three versus 105a) are clustered in a particular region (residues 155 to 305), which may therefore represent a domain that influences the choice of partner adaptin.

Adaptor Protein Complex 1↗

PubMed1996

Constitutively active mitogen-activated protein kinase kinase 1 (MAPKK1) and MAPKK2 mediate similar transcriptional and morphological responses.

Both mitogen-activated protein kinase kinase 1 (MAPKK1) and MAPKK2 function downstream of the proto-oncogene product Raf in signaling pathways that affect cell proliferation and differentiation. The isoforms were previously shown to be differentially regulated in two significant ways: (a) MAPKK1, but not MAPKK2, was phosphorylated and inactivated by the cyclin-dependent kinase p34cdc2; and (b) p21 Ras formed a ternary complex with Raf/MAPKK1 but not with Raf/MAPKK2. To further characterize the regulation and function of the two isoforms, we compared their mode of activation by v-Mos and examined the transcriptional and morphological responses that they mediate in cultured mammalian cells. v-Mos enhanced the enzymatic activity of both isoforms to the same extent, by about 600-fold. Constitutively active MAPKK2 mutants were generated by introducing the same deletion and amino acid substitutions that have been shown to activate MAPKK1, suggesting that the conformational changes that lead to their activation are analogous. These mutants potentiated transcription from a promoter containing AP1-responsive elements and induced morphological transformation when expressed in mammalian cells, matching outcomes observed with constitutively active MAPKK1. The specific activity of p42 MAPK in the transformed cells was 3-fold higher than in cells expressing wild-type MAPKK, thereby implicating p42 MAPK as a common effector in vivo, and suggesting that sustained activation of p42 MAPK may represent a critical factor that contributes to the development of the transformed state. Altogether, the results demonstrate that the two isoforms elicit similar responses in vivo despite differences in their regulation.

3T3 Cells↗

PubMed1996

In vivo phosphorylation of adaptors regulates their interaction with clathrin.

The coat proteins of clathrin-coated vesicles (CCV) spontaneously self-assemble in vitro, but, in vivo, their self-assembly must be regulated. To determine whether phosphorylation might influence coat formation in the cell, the in vivo phosphorylation state of CCV coat proteins was analyzed. Individual components of the CCV coat were isolated by immunoprecipitation from Madin-Darby bovine kidney cells, labeled with [32P]orthophosphate under normal culture conditions. The predominant phosphoproteins identified were subunits of the AP1 and AP2 adaptors. These included three of the four 100-kD adaptor subunits, alpha and beta 2 of AP2 and beta 1 of AP1, but not the gamma subunit of AP1. In addition, the mu 1 and mu 2 subunits of AP1 and AP2 were phosphorylated under these conditions. Lower levels of in vivo phosphorylation were detected for the clathrin heavy and light chains. Analysis of phosphorylation sites of the 100-kD adaptor subunits indicated they were phosphorylated on serines in their hinge regions, domains that have been implicated in clathrin binding. In vitro clathrin-binding assays revealed that, upon phosphorylation, adaptors no longer bind to clathrin. In vivo analysis further revealed that adaptors with phosphorylated 100-kD subunits predominated in the cytosol, in comparison with adaptors associated with cellular membranes, and that phosphorylated beta 2 subunits of AP2 were exclusively cytosolic. Kinase activity, which converts adaptors to a phosphorylated state in which they no longer bind clathrin, was found associated with the CCV coat. These results suggest that adaptor phosphorylation influences adaptor-clathrin interactions in vivo and could have a role in controlling coat disassembly and reassembly.

Adaptor Protein Complex 1↗

PubMed1998

UV irradiation induces the murine urokinase-type plasminogen activator gene via the c-Jun N-terminal kinase signaling pathway: requirement of an AP1 enhancer element.

UV irradiation leads to severe damage, such as cutaneous inflammation, immunosuppression, and cancer, but it also results in a gene induction protective response termed the UV response. The signal triggering the UV response was thought to originate from DNA damage; recent findings, however, have shown that it is initiated at or near the cell membrane and transmitted via cytoplasmic kinase cascades to induce gene transcription. Urokinase-type plasminogen activator (uPA) was the first protein shown to be UV inducible in xeroderma pigmentosum DNA repair-deficient human cells. However, the underlying molecular mechanisms responsible for the induction were not elucidated. We have found that the endogenous murine uPA gene product is transcriptionally upregulated by UV in NIH 3T3 fibroblast and F9 teratocarcinoma cells. This induction required an activator protein 1 (AP1) enhancer element located at -2.4 kb, since deletion of this site abrogated the induction. We analyzed the contribution of the three different types of UV-inducible mitogen-activated protein (MAP) kinases (ERK, JNK/SAPK, and p38) to the activation of the murine uPA promoter by UV. MEKK1, a specific JNK activator, induced transcription from the uPA promoter in the absence of UV treatment, whereas coexpression of catalytically inactive MEKK1(K432M) and of cytoplasmic JNK inhibitor JIP-1 inhibited UV-induced uPA transcriptional activity. In contrast, neither dominant negative MKK6 (or SB203580) nor PD98059, which specifically inhibit p38 and ERK MAP kinase pathways, respectively, could abrogate the UV-induced effect. Moreover, our results indicated that wild-type N-terminal c-Jun, but not mutated c-Jun (Ala-63/73), was able to mediate UV-induced uPA transcriptional activity. Taken together, we show for the first time that kinases of the JNK family can activate the uPA promoter. This activation links external UV stimulation and AP1-dependent uPA transcription, providing a transcription-coupled signal transduction pathway for the induction of the murine uPA gene by UV.

3T3 Cells↗

PubMed1996

Cooperation of protein disulfide isomerase and redox environment in the regulation of NF-kappaB and AP1 binding to DNA.

Most transcription factors are multimeric complexes whose subunits depend on strict conformation requirements to form the active unit. Among these requirements is the presence of appropriate sulfhydryl interactions that are critical to transcription factor binding to cognate DNA recognition sites. Our experiments now suggest that modulation of these sulfhydryls may involve the action of thiol-modifying oxido-reductases such as protein disulfide isomerase (PDI). Electrophoretic mobility shift titration experiments incorporating different ratios of GSH:GSSG indicated that changes in GSH and GSSG concentrations corresponding to redox potential differences of as little as +/- 15 mV enabled or abolished binding of NF-kappaB and AP1 to their cognate DNA sites. Moreover, this binding range was modulated significantly by the addition of purified protein disulfide isomerase (PDI). Collectively, these results suggest that a reversible oxidation/reduction signalling pathway may exist in the cell whereby localized changes in redox potentials and/or oxido-reductase activity can be functionally relevant in the regulation of critical gene expression events.

Adaptor Protein Complex 1↗

PubMed1994

The Saccharomyces cerevisiae APS1 gene encodes a homolog of the small subunit of the mammalian clathrin AP-1 complex: evidence for functional interaction with clathrin at the Golgi complex.

Clathrin-associated protein (AP) complexes have been implicated in the assembly of clathrin coats and the selectivity of clathrin-mediated protein transport processes. We have identified a yeast gene, APS1, encoding a homolog of the small (referred to herein as sigma) subunits of the mammalian AP-1 complex. Sequence comparisons have shown that Aps1p is more similar to the sigma subunit of the Golgi-localized mammalian AP-1 complex than Aps2p, which is more related to the plasma membrane AP-2 sigma subunit. Like their mammalian counterparts, Aps1p and Aps2p are components of distinct, large (> 200 kDa) complexes and a significant portion of the Aps proteins co-fractionate with clathrin-coated vesicles during gel filtration chromatography. Unexpectedly, even though the evolutionary conservation of AP small subunits is substantial (50% identity between mammalian and yeast proteins), disruptions of APS1 (aps1 delta) and APS2 (aps2 delta), individually or in combination, elicit no detectable mutant phenotypes. These data indicate that the Aps proteins are not absolutely required for clathrin-mediated selective protein transport in cells expressing wild type clathrin. However, aps1 delta accentuated the slow growth and alpha-factor pheromone maturation defect of cells carrying a temperature-sensitive allele of clathrin heavy chain (Chc) (chc1-ts). In contrast, aps1 delta did not influence the effects of chc1-ts on vacuolar protein sorting or receptor-mediated endocytosis. The aps2 delta mutation resulted in a slight effect on chc1-ts cell growth but had no additional effects. The growth defect of cells completely lacking Chc was compounded by aps1 delta but not aps2 delta. These results comprise evidence that Aps1p is involved in a subset of clathrin functions at the Golgi apparatus. The effect of aps1 delta on cells devoid of clathrin function suggests that Aps1p also participates in clathrin-independent processes.

Adaptor Protein Complex 1↗

PubMed2000

Adaptor gamma ear homology domain conserved in gamma-adaptin and GGA proteins that interact with gamma-synergin.

We identified a novel family of proteins that have a VHS domain and an AGEH (adaptor gamma ear homology) domain that is homologous to the ear domain of the gamma-adaptin subunit of the AP-1 clathrin adaptor. When overexpressed, the proteins, called GGA1, GGA2, and GGA3, localized to the trans-Golgi network (TGN) and often caused fragmentation and vacuolation of the compartment. Yeast two-hybrid analysis showed that the AGEH domains of the GGA proteins as well as those of gamma-adaptins are able to interact with gamma-synergin, which was previously shown to localized in the TGN region and interact with gamma-adaptin. Furthermore, gamma-synergin and either of the GGA proteins coexpressed were colocalized in the TGN region. These results suggest that the GGA proteins regulate the function of the TGN or membrane trafficking from this compartment and that the AGEH domains of GGAs and gamma-adaptins, like the ear domain of alpha-adaptin, are involved in interaction with molecules that modulate their functions.

ADP-Ribosylation Factors↗

PubMed1993

Relationship between apoptosis and the cell cycle in lymphocytes: roles of protein kinase C, tyrosine phosphorylation, and AP1.

The mechanism of switching between the cell cycle and active cell death (apoptosis) was investigated in cytokine-dependent CTLL cells. These cells proliferate in the presence of interleukin 2 (IL2), but accumulate in early G1 and undergo apoptosis in its absence. In the absence of IL2 the cells also become sensitive to glucocorticoid-induced apoptosis. Using specific inhibitors of protein kinase C and tyrosine kinases we established that two signals are required to fully repress cell death and stimulate G1 progression. One of these signals activates protein kinase C (PKC) which represses cell death and the other activates a tyrosine kinase which confers glucocorticoid resistance and permits cell cycle progression. Thus, phorbol esters can activate PKC and maintain cell viability in the absence of IL2, but the cells cannot proliferate. Moreover, the cells remain sensitive to glucocorticoid-induced apoptosis unless the tyrosine kinase-mediated signal is also given. There is a correlation between the presence of AP1 DNA-binding activity and the repression of the cell death pathway. The c-jun gene is expressed constitutively and both IL2 and phorbol esters induce the expression of c-fos to generate a functional AP1 capable of repressing cell death. However, only interleukin 2 can initiate the tyrosine kinase-mediated modification that confers dexamethasone resistance and permits G1 progression. In the absence of IL2 glucocorticoids stimulate AP1 degradation and induce apoptosis.

Adaptor Protein Complex 1↗

PubMed1996

Cloning and expression of a plant homologue of the small subunit of the Golgi-associated clathrin assembly protein AP19 from Camptotheca acuminata.

Clathrin-coated vesicles (CCVs) are involved in selective protein transport in eukaryotes. AP-1 and AP-2 are protein complexes found in the CCVs of the Golgi apparatus and the plasma membrane respectively. AP19 is the smallest polypeptide chain components of AP-1. We have identified a cDNA clone (CAP19) encoding a putative homologue for the assembly protein AP19 from the Chinese medicinal tree, Camptotheca acuminata. The deduced polypeptide contains 161 amino acids and has a predicted Mr of 18820. DNA blot analysis suggests that the AP19S of C. acuminata are encoded by a small gene family. CAP19 was expressed ubiquitously throughout the plant suggesting that it may be involved in general Golgi-mediated secretion.

Adaptor Protein Complex 1↗

PubMed1997

Characterization of the mouse beta-prime adaptin gene; cDNA sequence, genomic structure, and chromosomal localization.

Adaptins are important subunits of heterotetrameric complexes called adaptors, which participate in the clathrin-coated, vesicle-mediated endocytosis and intracellular receptor transport. The gene family of adaptins is divided into three classes, alpha, beta, and gamma, with further subdivision into beta- and beta-prime components. Two beta-prime adaptins, the rat AP105a and the human BAM22, have previously been characterized. The BAM22 gene is located on human Chromosome (Chr) 22q12 and can be considered a candidate meningioma tumor suppressor gene. We report here the characterization of the mouse ortholog of the BAM22 gene, and we suggest the name adtb1 for the mouse gene. Like the BAM22 gene, the adtb1 transcript is highly and ubiquitously expressed. We provide 3885-bp cDNA sequence, which entirely covers the open reading frame of the adtb1, capable of encoding a protein of 943 amino acids. The adtb1 protein is highly conserved (>96% identity) when compared with AP105a and BAM22 proteins. We also report the genomic organization of adtb1, which is similar to the BAM22 gene. The adtb1 gene has been assigned to mouse Chr 11, band 11A2, which confirms the synteny between human Chr 22q12 and mouse Chr 11.

Adaptor Protein Complex 1↗