RESUMO
Rab35 (Ras-associated binding protein) is a small GTPase that regulates endosomal membrane trafficking and functions in cell polarity, cytokinesis, and growth factor signaling. Altered Rab35 function contributes to progression of glioblastoma, defects in primary cilia formation, and altered cytokinesis. Here, we report a pediatric patient with global developmental delay, hydrocephalus, a Dandy-Walker malformation, axial hypotonia with peripheral hypertonia, visual problems, and conductive hearing impairment. Exome sequencing identified a homozygous missense variant in the GTPase fold of RAB35 (c.80G>A; p.R27H) as the most likely candidate. Functional analysis of the R27H-Rab35 variant protein revealed enhanced interaction with its guanine-nucleotide exchange factor, DENND1A and decreased interaction with a known effector, MICAL1, indicating that the protein is in an inactive conformation. Cellular expression of the variant drives the activation of Arf6, a small GTPase under negative regulatory control of Rab35. Importantly, variant expression leads to delayed cytokinesis and altered length, number, and Arl13b composition of primary cilia, known factors in neurodevelopmental disease. Our findings provide evidence of altered Rab35 function as a causative factor of a neurodevelopmental disorder.
Assuntos
Mutação de Sentido Incorreto , Transtornos do Neurodesenvolvimento , Proteínas rab de Ligação ao GTP , Feminino , Humanos , Masculino , Fator 6 de Ribosilação do ADP , Fatores de Ribosilação do ADP/genética , Fatores de Ribosilação do ADP/metabolismo , Linhagem Celular , Cílios/metabolismo , Cílios/genética , Cílios/patologia , Citocinese/genética , Fatores de Troca do Nucleotídeo Guanina/genética , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Mutação com Perda de Função , Transtornos do Neurodesenvolvimento/genética , Transtornos do Neurodesenvolvimento/metabolismo , Transtornos do Neurodesenvolvimento/patologia , Linhagem , Proteínas rab de Ligação ao GTP/genética , Proteínas rab de Ligação ao GTP/metabolismo , Modelos Moleculares , Estrutura Terciária de ProteínaRESUMO
BACKGROUND: De-escalation is often advocated to reduce harm associated with violence and use of restrictive interventions, but there is insufficient understanding of factors that influence de-escalation behaviour in practice. For the first time, using behaviour change and implementation science methodology, this paper aims to identify the drivers that will enhance de-escalation in acute inpatient and psychiatric intensive care mental health settings. METHODS: Secondary analysis of 46 qualitative interviews with ward staff (n = 20) and patients (n = 26) informed by the Theoretical Domains Framework. RESULTS: Capabilities for de-escalation included knowledge (impact of trauma on memory and self-regulation and the aetiology and experience of voice hearing) and skills (emotional self-regulation, distress validation, reducing social distance, confirming autonomy, setting limits and problem-solving). Opportunities for de-escalation were limited by dysfunctional risk management cultures/ relationships between ward staff and clinical leadership, and a lack of patient involvement in safety maintenance. Motivation to engage in de-escalation was limited by negative emotion associated with moral formulations of patients and internal attributions for behaviour. CONCLUSION: In addition to training that enhances knowledge and skills, interventions to enhance de-escalation should target ward and organisational cultures, as well as making fundamental changes to the social and physical structure of inpatient mental health wards. Psychological interventions targeting negative emotion in staff are needed to increase motivation. This paper provides a new evidence-based framework of indicative changes that will enhance de-escalation in adult acute mental health inpatient and PICU settings.
Assuntos
Agressão , Pacientes Internados , Pesquisa Qualitativa , Humanos , Masculino , Agressão/psicologia , Feminino , Adulto , Pacientes Internados/psicologia , Pessoa de Meia-Idade , Transtornos Mentais/psicologia , Transtornos Mentais/terapia , Unidade Hospitalar de Psiquiatria , Atitude do Pessoal de SaúdeRESUMO
Autosomal recessive spastic ataxia of Charlevoix-Saguenay is a fatal brain disorder featuring cerebellar neurodegeneration leading to spasticity and ataxia. This disease is caused by mutations in the SACS gene that encodes sacsin, a massive 4579-amino acid protein with multiple modular domains. However, molecular details of the function of sacsin are not clear. Here, using live cell imaging and biochemistry, we demonstrate that sacsin binds to microtubules and regulates microtubule dynamics. Loss of sacsin function in various cell types, including knockdown and KO primary neurons and patient fibroblasts, leads to alterations in lysosomal transport, positioning, function, and reformation following autophagy. Each of these phenotypic changes is consistent with altered microtubule dynamics. We further show the effects of sacsin are mediated at least in part through interactions with JIP3, an adapter for microtubule motors. These data reveal a new function for sacsin that explains its previously reported roles and phenotypes.
Assuntos
Proteínas de Choque Térmico , Lisossomos , Microtúbulos , Espasticidade Muscular , Ataxias Espinocerebelares , Sequência de Aminoácidos , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Lisossomos/genética , Lisossomos/metabolismo , Microtúbulos/genética , Microtúbulos/metabolismo , Espasticidade Muscular/genética , Espasticidade Muscular/metabolismo , Mutação , Ataxias Espinocerebelares/congênito , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismoRESUMO
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of COVID-19, so understanding its biology and infection mechanisms is critical to facing this major medical challenge. SARS-CoV-2 is known to use its spike glycoprotein to interact with the cell surface as a first step in the infection process. As for other coronaviruses, it is likely that SARS-CoV-2 next undergoes endocytosis, but whether or not this is required for infectivity and the precise endocytic mechanism used are unknown. Using purified spike glycoprotein and lentivirus pseudotyped with spike glycoprotein, a common model of SARS-CoV-2 infectivity, we now demonstrate that after engagement with the plasma membrane, SARS-CoV-2 undergoes rapid, clathrin-mediated endocytosis. This suggests that transfer of viral RNA to the cell cytosol occurs from the lumen of the endosomal system. Importantly, we further demonstrate that knockdown of clathrin heavy chain, which blocks clathrin-mediated endocytosis, reduces viral infectivity. These discoveries reveal that SARS-CoV-2 uses clathrin-mediated endocytosis to gain access into cells and suggests that this process is a key aspect of virus infectivity.
Assuntos
Enzima de Conversão de Angiotensina 2/genética , Cadeias Pesadas de Clatrina/genética , Endocitose/genética , SARS-CoV-2/genética , Glicoproteína da Espícula de Coronavírus/genética , Internalização do Vírus/efeitos dos fármacos , Células A549 , Enzima de Conversão de Angiotensina 2/metabolismo , Animais , Chlorocebus aethiops , Cadeias Pesadas de Clatrina/antagonistas & inibidores , Cadeias Pesadas de Clatrina/metabolismo , Endocitose/efeitos dos fármacos , Endossomos/efeitos dos fármacos , Endossomos/metabolismo , Endossomos/virologia , Regulação da Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Células HEK293 , Interações Hospedeiro-Patógeno/genética , Humanos , Hidrazonas/farmacologia , Lentivirus/genética , Lentivirus/metabolismo , Ligação Proteica/efeitos dos fármacos , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , SARS-CoV-2/efeitos dos fármacos , SARS-CoV-2/metabolismo , Transdução de Sinais , Glicoproteína da Espícula de Coronavírus/metabolismo , Sulfonamidas/farmacologia , Tiazolidinas/farmacologia , Células VeroRESUMO
BACKGROUND: Around 60 000 people in England live in mental health supported accommodation. There are three main types: residential care, supported housing and floating outreach. Supported housing and floating outreach aim to support service users in moving on to more independent accommodation within 2 years, but there has been little research investigating their effectiveness. AIMS: A 30-month prospective cohort study investigating outcomes for users of mental health supported accommodation. METHOD: We used random sampling, accounting for relevant geographical variation factors, to recruit 87 services (22 residential care, 35 supported housing and 30 floating outreach) and 619 service users (residential care 159, supported housing 251, floating outreach 209) across England. We contacted services every 3 months to investigate the proportion of service users who successfully moved on to more independent accommodation. Multilevel modelling was used to estimate how much of the outcome and cost variations were due to service type and quality, after accounting for service-user characteristics. RESULTS: Overall 243/586 participants successfully moved on (residential care 15/146, supported housing 96/244, floating outreach 132/196). This was most likely for floating outreach service users (versus residential care: odds ratio 7.96, 95% CI 2.92-21.69, P < 0.001; versus supported housing: odds ratio 2.74, 95% CI 1.01-7.41, P < 0.001) and was associated with reduced costs of care and two aspects of service quality: promotion of human rights and recovery-based practice. CONCLUSIONS: Most people do not move on from supported accommodation within the expected time frame. Greater focus on human rights and recovery-based practice may increase service effectiveness.
Assuntos
Habitação/estatística & dados numéricos , Transtornos Mentais , Serviços de Saúde Mental/estatística & dados numéricos , Inglaterra , Feminino , Custos de Cuidados de Saúde , Habitação/economia , Direitos Humanos , Humanos , Masculino , Transtornos Mentais/economia , Serviços de Saúde Mental/economia , Razão de Chances , Estudos Prospectivos , Fatores de TempoRESUMO
Rab GTPases are key regulators of membrane trafficking, and many are activated by guanine nucleotide exchange factors bearing a differentially expressed in normal and neoplastic cells (DENN) domain. By activating the small GTPase Rab12, DENN domain-containing protein 3 (DENND3) functions in autophagy. Here, we identified a structural domain (which we name PHenn) containing a pleckstrin homology subdomain that binds actin and is required for DENND3 function in autophagy. We found that a hydrophobic patch on an extended ß-turn of the PHenn domain mediates an intramolecular interaction with the DENN domain of DENND3. We also show that DENND3 binds actin through a surface of positively charged residues on the PHenn domain. Substitutions that blocked either DENN or actin binding compromised the role of DENND3 in autophagy. These results provide new mechanistic insight into the structural determinants regulating DENND3 in autophagy and lay the foundation for future investigations of the DENN protein family.
Assuntos
Actinas/metabolismo , Autofagia , Proteínas Sanguíneas/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Fosfoproteínas/metabolismo , Proteínas rab de Ligação ao GTP/metabolismo , Actinas/química , Actinas/genética , Proteínas Sanguíneas/química , Cristalografia por Raios X , Fatores de Troca do Nucleotídeo Guanina/química , Fatores de Troca do Nucleotídeo Guanina/genética , Células HEK293 , Humanos , Fosfoproteínas/química , Fosforilação , Ligação Proteica , Conformação Proteica , Domínios Proteicos , Proteínas rab de Ligação ao GTP/química , Proteínas rab de Ligação ao GTP/genéticaRESUMO
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disease that is caused by mutations in the SACS gene. The product of this gene is a very large 520-kDa cytoplasmic protein, sacsin, with a ubiquitin-like (Ubl) domain at the N terminus followed by three large sacsin internal repeat (SIRPT) supradomains and C-terminal J and HEPN domains. The SIRPTs are predicted to contain Hsp90-like domains, suggesting a potential chaperone activity. In this work, we report the structures of the Hsp90-like Sr1 domain of SIRPT1 and the N-terminal Ubl domain determined at 1.55- and 2.1-Å resolutions, respectively. The Ubl domain crystallized as a swapped dimer that could be relevant in the context of full-length protein. The Sr1 domain displays the Bergerat protein fold with a characteristic nucleotide-binding pocket, although it binds nucleotides with very low affinity. The Sr1 structure reveals that ARSACS-causing missense mutations (R272H, R272C, and T201K) disrupt protein folding, most likely leading to sacsin degradation. This work lends structural support to the view of sacsin as a molecular chaperone and provides a framework for future studies of this protein.
Assuntos
Proteínas de Choque Térmico/química , Mutação de Sentido Incorreto , Dobramento de Proteína , Substituição de Aminoácidos , Cristalografia por Raios X , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Humanos , Espasticidade Muscular/genética , Espasticidade Muscular/metabolismo , Domínios Proteicos , Ataxias Espinocerebelares/congênito , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismoRESUMO
Epileptic encephalopathies are a catastrophic group of epilepsies characterized by refractory seizures and cognitive arrest, often resulting from abnormal brain development. Here, we have identified an epileptic encephalopathy additionally featuring cerebral calcifications and coarse facial features caused by recessive loss-of-function mutations in DENND5A. DENND5A contains a DENN domain, an evolutionarily ancient enzymatic module conferring guanine nucleotide exchange factor (GEF) activity to multiple proteins serving as GEFs for Rabs, which are key regulators of membrane trafficking. DENND5A is detected predominantly in neuronal tissues, and its highest levels occur during development. Knockdown of DENND5A leads to striking alterations in neuronal development. Mechanistically, these changes appear to result from upregulation of neurotrophin receptors, leading to enhanced downstream signaling. Thus, we have identified a link between a DENN domain protein and neuronal development, dysfunction of which is responsible for a form of epileptic encephalopathy.
Assuntos
Encéfalo/patologia , Epilepsia/genética , Mutação , Proteínas rab de Ligação ao GTP/genética , Adolescente , Animais , Criança , Consanguinidade , Feminino , Fatores de Troca do Nucleotídeo Guanina , Humanos , Masculino , Neurônios/metabolismo , Células PC12 , Linhagem , RatosRESUMO
Epidermal growth factor (EGF) activates the EGF receptor (EGFR) and stimulates its internalization and trafficking to lysosomes for degradation. However, a percentage of EGFR undergoes ligand-independent endocytosis and is rapidly recycled back to the plasma membrane. Importantly, alterations in EGFR recycling are a common hallmark of cancer, and yet, our understanding of the machineries controlling the fate of endocytosed EGFR is incomplete. Intersectin-s is a multi-domain adaptor protein that is required for internalization of EGFR Here, we discover that intersectin-s binds DENND2B, a guanine nucleotide exchange factor for the exocytic GTPase Rab13, and this interaction promotes recycling of ligand-free EGFR to the cell surface. Intriguingly, upon EGF treatment, DENND2B is phosphorylated by protein kinase D and dissociates from intersectin-s, allowing for receptor targeting to degradation. Our study thus reveals a novel mechanism controlling the fate of internalized EGFR with important implications for cancer.
Assuntos
Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Fator de Crescimento Epidérmico/metabolismo , Receptores ErbB/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Transdução de Sinais , Proteínas Supressoras de Tumor/metabolismo , Membrana Celular/metabolismo , Endocitose , Fator de Crescimento Epidérmico/farmacologia , Receptores ErbB/efeitos dos fármacos , Receptores ErbB/genética , Fatores de Troca do Nucleotídeo Guanina/genética , Células HEK293 , Humanos , Neoplasias/fisiopatologia , Fosforilação , Ligação Proteica , Proteína Quinase C/metabolismo , Transporte Proteico , Proteínas Supressoras de Tumor/genética , Proteínas rab de Ligação ao GTP/metabolismoRESUMO
The Rab family of small GTPases functions in multiple aspects of cellular membrane trafficking. Proteins bearing a differentially expressed in normal and neoplastic cells (DENN) domain have emerged as the largest family of Rab-activating guanine nucleotide exchange factors (GEFs). Rab12 functions in the initiation of starvation-induced autophagy, and our previous work revealed that its activator, DENN domain-containing protein 3 (DENND3), is phosphorylated and activated upon starvation. However, how the GEF activity of DENND3 toward Rab12 is regulated at the molecular level is still not understood. Here, we combine size-exclusion chromatography, Förster resonance energy transfer, pulldown, and in vitro GEF assays to demonstrate that regulation of GEF activity is achieved through an intramolecular interaction that is controlled by a key residue in DENND3, tyrosine 940. Our study sheds light on the regulation of Rab12 activation and lays the groundwork for characterizing the regulation of other DENN domain-containing proteins.
Assuntos
Fatores de Troca do Nucleotídeo Guanina/metabolismo , Proteínas rab de Ligação ao GTP/metabolismo , Animais , Autofagia , Membrana Celular/metabolismo , Cromatografia , Transferência Ressonante de Energia de Fluorescência , Guanosina Difosfato/química , Guanosina Trifosfato/química , Células HEK293 , Células HeLa , Humanos , Imunoprecipitação , Camundongos , Microscopia de Fluorescência , Mutação , Fosforilação , Ligação Proteica , Domínios Proteicos , Tirosina/químicaRESUMO
BACKGROUND: Post-deinstitutionalisation, mental health supported accommodation services have been implemented widely. The available research evidence is heterogeneous in nature and resistant to synthesis attempts, leaving researchers and policy makers with no clear summary what works and for whom. In this context, we undertook a comprehensive systematic review of quantitative studies in order to synthesise the current evidence on mental health and psychosocial outcomes for individuals residing in mental health supported accommodation services. METHODS: Using a combination of electronic database searches, hand searches, forward-backward snowballing and article recommendations from an expert panel, 115 papers were identified for review. Data extraction and quality assessments were conducted, and 33 articles were excluded due to low quality, leaving 82 papers in the final review. Variation in terminology and service characteristics made the comparison of service models unfeasible. As such, findings were presented according to the following sub-groups: 'Homeless', 'Deinstitutionalisation' and 'General Severe Mental Illness (SMI)'. RESULTS: Results were mixed, reflecting the heterogeneity of the supported accommodation literature, in terms of research quality, experimental design, population, service types and outcomes assessed. There is some evidence that supported accommodation is effective across a range of psychosocial outcomes. The most robust evidence supports the effectiveness of the permanent supported accommodation model for homeless SMI in generating improvements in housing retention and stability, and appropriate use of clinical services over time, and for other forms of supported accommodation for deinstitutionalised populations in reducing hospitalisation rates and improving appropriate service use. The evidence base for general SMI populations is less developed, and requires further research. CONCLUSIONS: A lack of high-quality experimental studies, definitional inconsistency and poor reporting continue to stymie our ability to identify effective supported accommodation models and practices. The authors recommend improved reporting standards and the prioritisation of experimental studies that compare outcomes across different service models.
Assuntos
Desinstitucionalização/métodos , Habitação , Transtornos Mentais/reabilitação , Serviços de Saúde Mental , Reabilitação Psiquiátrica/métodos , Humanos , Reabilitação Psiquiátrica/psicologiaRESUMO
The DENN domain is an evolutionarily ancient protein module. Mutations in the DENN domain cause developmental defects in plants and human diseases, yet the function of this common module is unknown. We now demonstrate that the connecdenn/DENND1A DENN domain functions as a guanine nucleotide exchange factor (GEF) for Rab35 to regulate endosomal membrane trafficking. Loss of Rab35 activity causes an enlargement of early endosomes and inhibits MHC class I recycling. Moreover, it prevents early endosomal recruitment of EHD1, a common component of tubules involved in endosomal cargo recycling. Our data reveal an enzymatic activity for a DENN domain and demonstrate that distinct Rab GTPases can recruit a common protein machinery to various sites within the endosomal network to establish cargo-selective recycling pathways.
Assuntos
Endossomos/metabolismo , Fatores de Troca do Nucleotídeo Guanina/fisiologia , Proteínas rab de Ligação ao GTP/fisiologia , Animais , Transporte Biológico , Células COS , Chlorocebus aethiops , Vesículas Revestidas por Clatrina/metabolismo , Endocitose , Fatores de Troca do Nucleotídeo Guanina/química , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Humanos , Mapeamento de Interação de Proteínas , Estrutura Terciária de Proteína , Ratos , Proteínas rab de Ligação ao GTP/química , Proteínas rab de Ligação ao GTP/metabolismoRESUMO
The members of the Rab family of GTPases are master regulators of cellular membrane trafficking. With â¼70 members in humans, Rabs have been implicated in all steps of membrane trafficking ranging from vesicle formation and transport to vesicle docking/tethering and fusion. Vesicle trafficking controls the localization and levels of a myriad of proteins, thus regulating cellular functions including proliferation, metabolism, cell-cell adhesion, and cell migration. It is therefore not surprising that impairment of Rab pathways is associated with diseases including cancer. In this review, we highlight evidence supporting the role of Rab13 as a potent driver of cancer progression.
Assuntos
Membrana Celular/metabolismo , Proliferação de Células , Proteínas de Neoplasias/metabolismo , Transdução de Sinais , Proteínas rab de Ligação ao GTP/metabolismo , Animais , Transporte Biológico Ativo , Membrana Celular/genética , Membrana Celular/patologia , Humanos , Proteínas de Neoplasias/genética , Neoplasias , Proteínas rab de Ligação ao GTP/genéticaRESUMO
Rab GTPases are critical regulators of membrane trafficking. The canonical view is that Rabs are soluble in their inactive GDP-bound form, and only upon activation and conversion to their GTP-bound state are they anchored to membranes through membrane insertion of a C-terminal prenyl group. Here we demonstrate that C-terminal prenylation is not required for Rab13 to associate with and traffic on vesicles. Instead, inactive Rab13 appears to associate with vesicles via protein-protein interactions. Only following activation does Rab13 associate with the plasma membrane, presumably with insertion of the C-terminal prenyl group into the membrane.
Assuntos
Proteínas rab de Ligação ao GTP/metabolismo , Substituição de Aminoácidos , Animais , Linhagem Celular , Estruturas da Membrana Celular/metabolismo , Vesículas Citoplasmáticas/metabolismo , Endossomos/metabolismo , Inibidores de Dissociação do Nucleotídeo Guanina/metabolismo , Células HEK293 , Humanos , Modelos Biológicos , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Domínios e Motivos de Interação entre Proteínas , Prenilação de Proteína , Transporte Proteico , Ratos , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Análise de Célula Única , Proteínas rab de Ligação ao GTP/química , Proteínas rab de Ligação ao GTP/genéticaRESUMO
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS [MIM 270550]) is an early-onset neurodegenerative disorder caused by mutations in the SACS gene. Over 170 SACS mutations have been reported worldwide and are thought to cause loss of function of sacsin, a poorly characterized and massive 520 kDa protein. To establish an animal model and to examine the pathophysiological basis of ARSACS, we generated Sacs knockout (Sacs(-/-)) mice. Null animals displayed an abnormal gait with progressive motor, cerebellar and peripheral nerve dysfunctions highly reminiscent of ARSACS. These clinical features were accompanied by an early onset, progressive loss of cerebellar Purkinje cells followed by spinal motor neuron loss and peripheral neuropathy. Importantly, loss of sacsin function resulted in abnormal accumulation of non-phosphorylated neurofilament (NF) bundles in the somatodendritic regions of vulnerable neuronal populations, a phenotype also observed in an ARSACS brain. Moreover, motor neurons cultured from Sacs(-/-) embryos exhibited a similar NF rearrangement with significant reduction in mitochondrial motility and elongated mitochondria. The data points to alterations in the NF cytoskeleton and defects in mitochondrial dynamics as the underlying pathophysiological basis of ARSACS.
Assuntos
Proteínas de Choque Térmico/genética , Mitocôndrias/patologia , Neurônios Motores/patologia , Espasticidade Muscular/fisiopatologia , Células de Purkinje/patologia , Ataxias Espinocerebelares/congênito , Animais , Modelos Animais de Doenças , Proteínas de Choque Térmico/metabolismo , Humanos , Filamentos Intermediários/patologia , Camundongos , Camundongos Knockout , Neurônios Motores/citologia , Espasticidade Muscular/genética , Células de Purkinje/metabolismo , Tratos Piramidais/patologia , Coluna Vertebral/patologia , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/fisiopatologia , Técnicas de Cultura de TecidosRESUMO
Synaptotagmin 1 (Syt1) is a synaptic vesicle protein that is important for the kinetics of both exocytosis and endocytosis, and is thus a candidate molecule to link these two processes. Although the tandem Ca(2+)-binding C2 domains of Syt1 have important roles in exocytosis and endocytosis, the function of the conserved juxtamembrane (jxm) linker region has yet to be determined. We now demonstrate that the jxm region of Syt1 interacts directly with the pleckstrin homology (PH) domain of the endocytic protein dynamin 1. By using cell-attached capacitance recordings with millisecond time resolution to monitor clathrin-mediated endocytosis of single vesicles in neuroendocrine chromaffin cells, we find that loss of this interaction prolongs the lifetime of the fission pore leading to defects in the dynamics of vesicle fission. These results indicate a previously undescribed interaction between two major regulatory proteins in the secretory vesicle cycle and that this interaction regulates endocytosis.
Assuntos
Encéfalo/metabolismo , Células Cromafins/metabolismo , Dinamina I/metabolismo , Vesículas Sinápticas/fisiologia , Sinaptotagmina I/fisiologia , Sequência de Aminoácidos , Animais , Western Blotting , Encéfalo/citologia , Cálcio/metabolismo , Membrana Celular/metabolismo , Células Cultivadas , Células Cromafins/citologia , Clatrina/metabolismo , Endocitose/fisiologia , Exocitose/fisiologia , Feminino , Humanos , Imunoprecipitação , Masculino , Camundongos , Camundongos Knockout , Dados de Sequência Molecular , Domínios e Motivos de Interação entre Proteínas , Ratos , Homologia de Sequência de Aminoácidos , Sinapses/fisiologiaRESUMO
Unc-51-like kinases (ULKs) are the most upstream kinases in the initiation of autophagy, yet the molecular mechanisms underlying their function are poorly understood. We report a new role for ULK in the induction of autophagy. ULK-mediated phosphorylation of the guanine nucleotide exchange factor DENND3 at serines 554 and 572 upregulates its GEF activity toward the small GTPase Rab12. Through binding to LC3 and associating with LC3-positive autophagosomes, active Rab12 facilitates autophagosome trafficking, thus establishing a crucial role for the ULK/DENND3/Rab12 axis in starvation-induced autophagy.
Assuntos
Autofagia , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas rab de Ligação ao GTP/metabolismo , Proteína Homóloga à Proteína-1 Relacionada à Autofagia , Técnicas de Silenciamento de Genes , Fatores de Troca do Nucleotídeo Guanina/genética , Células HEK293 , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Fagossomos/metabolismo , Fosforilação , Proteínas Serina-Treonina Quinases/genética , Transporte Proteico , RNA Interferente Pequeno , Proteínas rab de Ligação ao GTP/genéticaRESUMO
Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of dominant-inherited Parkinson's disease (PD), and yet we do not fully understand the physiological function(s) of LRRK2. Various components of the clathrin machinery have been recently found mutated in familial forms of PD. Here, we provide molecular insight into the association of LRRK2 with the clathrin machinery. We report that through its GTPase domain, LRRK2 binds directly to clathrin-light chains (CLCs). Using genome-edited HA-LRRK2 cells, we localize LRRK2 to endosomes on the degradative pathway, where it partially co-localizes with CLCs. Knockdown of CLCs and/or LRRK2 enhances the activation of the small GTPase Rac1, leading to alterations in cell morphology, including the disruption of neuronal dendritic spines. In Drosphila, a minimal rough eye phenotype caused by overexpression of Rac1, is dramatically enhanced by loss of function of CLC and LRRK2 homologues, confirming the importance of this pathway in vivo. Our data identify a new pathway in which CLCs function with LRRK2 to control Rac1 activation on endosomes, providing a new link between the clathrin machinery, the cytoskeleton and PD.