RESUMO
The established primary trigger of Alzheimer's disease's is ß-amyloid (Aß) (Mucke and Selkoe, 2012). Amyloid precursor protein (APP) endocytosis is required for Aß generation at early endosomes (Rajendran and Annaert, 2012). APP retention at endosomes also depends on its recycling back to the plasma membrane ( Koo et al., 1996 ; Ubelmann et al., 2017 ). The following recycling assay has been optimized to assess APP recycling by live murine Neuro2a cells, a neuroblastoma cell line ( Ubelmann et al., 2017 ).
RESUMO
The mechanisms driving pathological beta-amyloid (Aß) generation in late-onset Alzheimer's disease (AD) are unclear. Two late-onset AD risk factors, Bin1 and CD2AP, are regulators of endocytic trafficking, but it is unclear how their endocytic function regulates Aß generation in neurons. We identify a novel neuron-specific polarisation of Aß generation controlled by Bin1 and CD2AP We discover that Bin1 and CD2AP control Aß generation in axonal and dendritic early endosomes, respectively. Both Bin1 loss of function and CD2AP loss of function raise Aß generation by increasing APP and BACE1 convergence in early endosomes, however via distinct sorting events. When Bin1 levels are reduced, BACE1 is trapped in tubules of early endosomes and fails to recycle in axons. When CD2AP levels are reduced, APP is trapped at the limiting membrane of early endosomes and fails to be sorted for degradation in dendrites. Hence, Bin1 and CD2AP keep APP and BACE1 apart in early endosomes by distinct mechanisms in axon and dendrites. Individuals carrying variants of either factor would slowly accumulate Aß in neurons increasing the risk for late-onset AD.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Peptídeos beta-Amiloides/metabolismo , Proteínas do Citoesqueleto/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Secretases da Proteína Precursora do Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Ácido Aspártico Endopeptidases/metabolismo , Axônios/metabolismo , Membrana Celular/metabolismo , Endocitose , Endossomos , Feminino , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Masculino , Camundongos , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Transporte Proteico , Proteínas Supressoras de Tumor/genéticaRESUMO
Salmonella invasion of intestinal epithelial cells requires extensive, though transient, actin modifications at the site of bacterial entry. The actin-modifying protein villin is present in the brush border where it participates in the constitution of microvilli and in epithelial restitution after damage through its actin-severing activity. We investigated a possible role for villin in Salmonella invasion. The absence of villin, which is normally located at the bacterial entry site, leads to a decrease in Salmonella invasion. Villin is necessary for early membrane-associated processes and for optimal ruffle assembly by balancing the steady-state level of actin. The severing activity of villin is important for Salmonella invasion in vivo. The bacterial phosphatase SptP tightly regulates villin phosphorylation, while the actin-binding effector SipA protects F-actin and counterbalances villin-severing activity. Thus, villin plays an important role in establishing the balance between actin polymerization and actin severing to facilitate the initial steps of Salmonella entry.