Huntingtin-associated protein 1 regulates inhibitory synaptic transmission by modulating γ-aminobutyric acid type A receptor membrane trafficking

Kittler, Josef T.; Thomas, Philip; Tretter, Verena; Bogdanov, Yury; Haucke, Volker; Smart, Trevor G.; Moss, Stephen J.

doi:10.1073/pnas.0401860101

Cited by 204 publications

(207 citation statements)

References 38 publications

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“…Thus, we concluded that Hap1 not only sequesters but also stabilizes Dcaf7 in the cytoplasm by inhibiting its degradation by the UPS. Because Hap1 can protect internalized receptors from lysosomal degradation (11,(29)(30)(31), Hap1 may stabilize its binding partners from subsequent degradation through either the lysosome or UPS.…”

Section: Hap1 Stabilizes the Protein Level Of Dcaf7 By Inhibiting Itsmentioning

confidence: 99%

DYRK1A regulates Hap1–Dcaf7/WDR68 binding with implication for delayed growth in Down syndrome

Xiang

Ning

et al. 2017

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

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Huntingtin-associated protein 1 (Hap1) is known to be critical for postnatal hypothalamic function and growth. Hap1 forms stigmoid bodies (SBs), unique neuronal cytoplasmic inclusions of unknown function that are enriched in hypothalamic neurons. Here we developed a simple strategy to isolate the SB-enriched fraction from mouse brain. By analyzing Hap1 immunoprecipitants from this fraction, we identified a Hap1-interacting SB component, DDB1 and CUL4 associated factor 7 (Dcaf7)/WD40 repeat 68 (WDR68), whose protein level and nuclear translocation are regulated by Hap1. Moreover, we found that Hap1 bound Dcaf7 competitively in cytoplasm with dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A), a protein implicated in Down syndrome (DS). Depleting Hap1 promoted the DYRK1A-Dcaf7 interaction and increased the DYRK1A protein level. Transgenic DS mice overexpressing DYRK1A showed reduced Hap1-Dcaf7 association in the hypothalamus. Furthermore, the overexpression of DYRK1A in the hypothalamus led to delayed growth in postnatal mice, suggesting that DYRK1A regulates the Hap1-Dcaf7 interaction and postnatal growth and that targeting Hap1 or Dcaf7 could ameliorate growth retardation in DS.H untingtin-associated protein 1 (Hap1) is a cytoplasmic protein highly expressed in neurons of the CNS (1, 2). Hap1 was initially recognized for its binding to polyglutamine-expanded huntingtin (Htt), the protein responsible for Huntington's disease (3). Because Hap1 is expressed at various levels in different types of neurons (1,(4)(5)(6)(7)(8), it is likely involved in cell type-specific functions of the brain. For example, Hap1 is abundantly expressed in the hypothalamus, and its expression in the hypothalamus influences the central control of feeding (9); as a direct result, mice lacking Hap1 are malnourished and die in the early postnatal period (5, 10, 11). The function of Hap1 is also age dependent and appears to be important for postnatal neurogenesis in the paraventricular nuclei, the lateral hypothalamus (5, 11), and the dentate gyrus of the hippocampus (7).The specific function of Hap1 in the hypothalamus may be associated with unique cytoplasmic structures called "stigmoid bodies" (SBs), which are formed by Hap1 in the hypothalamus (12, 13) and appear to be non-membrane-bound, ovoid to circular in shape, and 0.5-3 μm in diameter (14,15). Widely regarded as a determinant marker for SBs, Hap1 is capable of sequestering several important disease-related proteins into SB-like inclusions in cell cultures, including Abelson helper integration site 1 (Ahi1), androgen receptor, TBP, and ataxin-3 (6, 16-18). However, in vivo evidence for such sequestration exists only for Ahi1, which is responsible for specific forms of Joubert syndrome. Other proteins, such as SorLA/LR11, sortilin, 5-HT 7 receptor, and 14-3-3, are also reported to be associated with . Although SBs are abundant in the hypothalamus, their functions remain elusive, despite speculation that they might be involved in sex-steroid maturation (15). We bel...

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Section: Hap1 Stabilizes the Protein Level Of Dcaf7 By Inhibiting Itsmentioning

confidence: 99%

DYRK1A regulates Hap1–Dcaf7/WDR68 binding with implication for delayed growth in Down syndrome

Xiang

Ning

et al. 2017

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

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“…Endocytic recycling assays were performed essentially as described (Ehlers, 2000;Kittler et al, 2004). For measurements of total surface expression, cortical neurons (DIV 10-13, ≥ 3 replicate 6-cm plates/genotype) were incubated for 30 min with 100 μg/ml leupeptin in media, washed with PBS (+ CaCl 2 /MgCl 2 ), followed by incubation with 1 mg/ml sulfo-NHS-SS-biotin (Pierce, Rockford, IL) in PBS for 20 min on ice.…”

Section: Analysis Of Endocytic Recycling By Surface Biotinylation Of mentioning

confidence: 99%

Calcium-modulating cyclophilin ligand regulates membrane trafficking of postsynaptic GABAA receptors

Yao

Norris

et al. 2008

Molecular and Cellular Neuroscience

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Accumulation of GABA A receptors (GABA A Rs) at GABAergic synapses requires the cytoplasmic loop region and C-terminal transmembrane domain of the receptor γ2 subunit. We here report a novel interaction of γ2 with Calcium-Modulating cyclophilin Ligand (CAML), an integral membrane protein that regulates this mechanism. Interaction of GABA A Rs with CAML depends on both the cytoplasmic region and fourth transmembrane domain of the γ2 subunit, CAML immunoprecipitates with GABA A Rs from transfected cells and brain lysates and colocalizes with γ2 in ER vesicles in soma and dendrites of neurons. CAML shRNA treatment results in reduced expression of postsynaptic GABA A Rs, along with significant reductions in GABA-evoked whole-cell currents and GABAergic synaptic function, while glutamatergic transmission is unaffected. Reduced surface expression of GABA A Rs in CAML mutant neurons is associated with selective deficits in recycling of endocytosed GABA A Rs to the cell surface. Our results indicate a specific role of CAML in functional expression and endocytic recycling of postsynaptic GABA A Rs.

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“…Upon internalization, receptors are either reinserted into the plasma membrane or targeted for degradation (10). The balance between these two processes is critical for determining the number of receptors expressed at synapses and hence neuronal excitability (11).…”

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confidence: 99%

“…All cell types were transfected by nucleofection as described in ref. 10. See SI Materials and Methods.…”

mentioning

confidence: 99%

“…Whole-cell recordings of mIPSCs from cortical slices, or GFP-2FYVE transfected cultured cortical cells, were performed using standard voltage clamp techniques in the presence of CNQX (20 M) and APV (40 M) to block AMPA and NMDA receptors, respectively (43,44). Membrane currents from HEK-293 cells were measured, as outlined previously at 32°C (10,43,45). Data were collected 5 min after obtaining a stable recording conformation.…”

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confidence: 99%

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Ubiquitin-dependent lysosomal targeting of GABA _A receptors regulates neuronal inhibition

Arancibia-Cárcamo

Yuen

Muir

et al. 2009

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

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The strength of synaptic inhibition depends partly on the number of GABA A receptors (GABAARs) found at synaptic sites. The trafficking of GABA ARs within the endocytic pathway is a key determinant of surface GABA AR number and is altered in neuropathologies, such as cerebral ischemia. However, the molecular mechanisms and signaling pathways that regulate this trafficking are poorly understood. Here, we report the subunit specific lysosomal targeting of synaptic GABA ARs. We demonstrate that the targeting of synaptic GABAARs into the degradation pathway is facilitated by ubiquitination of a motif within the intracellular domain of the ␥2 subunit. Blockade of lysosomal activity or disruption of the trafficking of ubiquitinated cargo to lysosomes specifically increases the efficacy of synaptic inhibition without altering excitatory currents. Moreover, mutation of the ubiquitination site within the ␥2 subunit retards the lysosomal targeting of GABA ARs and is sufficient to block the loss of synaptic GABA ARs after anoxic insult. Together, our results establish a previously unknown mechanism for influencing inhibitory transmission under normal and pathological conditions. endocytosis ͉ trafficking ͉ ischemia ͉ ion channels ͉ synapse T he strength of inhibitory synapses is a major determinant of neuronal processing and excitability and can be determined by the number of ␥-amino butyric acid type A receptors (GABA A Rs) found at synaptic sites (1-3). Moreover, in a number of neuropathologies, including status epilepticus and in vitro and in vivo models of cerebral ischemia, the rapid downmodulation of synaptic GABA A Rs has been reported to contribute to pathological disinhibition, excitotoxicity, and cell death (4-8). However, the molecular mechanisms and signaling pathways that regulate GABA A R trafficking, under normal or pathological conditions, remain unclear.GABA A Rs undergo significant rates of endocytosis, a process that can rapidly modify receptor number at synapses (9). Upon internalization, receptors are either reinserted into the plasma membrane or targeted for degradation (10). The balance between these two processes is critical for determining the number of receptors expressed at synapses and hence neuronal excitability (11). However, the regulatory mechanisms that control this endocytic sorting of synaptic GABA A Rs remain unknown.The trafficking of membrane proteins can be regulated via the covalent attachment of the 76 amino acid (aa) peptide, ubiquitin, or ubiquitin-like proteins to lysine residues within target proteins (12,13). A number of studies on the role of ubiquitination in regulating synaptic function under normal conditions and in pathological conditions such as ischemia have focused on the ubiquitin-proteasome system (14-18). However, within the endocytic pathway, mono-ubiquitination (or the addition of short ubiquitin chains) is a key signal that results in the specific targeting of cargo to late endosomes for subsequent lysosomal degradation (12,19,20). The significance of ubiquitinati...

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Huntingtin-associated protein 1 regulates inhibitory synaptic transmission by modulating γ-aminobutyric acid type A receptor membrane trafficking

Cited by 204 publications

References 38 publications

DYRK1A regulates Hap1–Dcaf7/WDR68 binding with implication for delayed growth in Down syndrome

DYRK1A regulates Hap1–Dcaf7/WDR68 binding with implication for delayed growth in Down syndrome

Calcium-modulating cyclophilin ligand regulates membrane trafficking of postsynaptic GABAA receptors

Ubiquitin-dependent lysosomal targeting of GABA _A receptors regulates neuronal inhibition

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Huntingtin-associated protein 1 regulates inhibitory synaptic transmission by modulating γ-aminobutyric acid type A receptor membrane trafficking

Cited by 204 publications

References 38 publications

DYRK1A regulates Hap1–Dcaf7/WDR68 binding with implication for delayed growth in Down syndrome

DYRK1A regulates Hap1–Dcaf7/WDR68 binding with implication for delayed growth in Down syndrome

Calcium-modulating cyclophilin ligand regulates membrane trafficking of postsynaptic GABAA receptors

Ubiquitin-dependent lysosomal targeting of GABA A receptors regulates neuronal inhibition

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Ubiquitin-dependent lysosomal targeting of GABA _A receptors regulates neuronal inhibition