Uncovering the mechanism of CD2AP behind Alzheimer’s disease

• Autor(a) principal: Piconêz, Tiago
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/147637
• topic: Alzheimer’s Disease; Intracellular trafficking; CD2AP; actin cytoskeleton; Arp 2/3 complex; Ciências Médicas

Disease (AD) is the most common form of dementia, where the key initiator is the excessive production of amyloid beta (Aβ). Aβ production from the processing of amyloid precursor protein (APP) by BACE1 and γ-secretase happens on the membrane of the endosomes when APP is not sorted for lysosomal degradation. Previously, CD2-associated protein (CD2AP), an AD genetic risk factor, was implicated in endocytic trafficking and actin cytoskeleton dynamics. In neurons, CD2AP promotes APP endosomal sorting for degradation and, thus, regulates amyloid beta production. However, whether the regulation of F-actin by CD2AP is required for APP sorting is unknown. Previous work found that interfering with the Actin-Related Protein 2/3 (ARP 2/3) complex containing the ARPC1A isoform may recapitulate the loss of endosomal F-actin induced by CD2AP depletion. We hypothesize that the ARP 2/3 complex containing the ARPC1A isoform acts with the CD2AP to stabilize endosomal branched F- actin to mediate APP endosomal sorting. Using N2a cell line transfected with siRNA against CD2AP or the ARPC1A isoform, together with immunofluorescence, trafficking assays, and live imaging, we found that ARPC1A loss of function leads to a specific decrease in perinuclear F-actin in a likewise manner to CD2AP loss of function. Importantly, ARPC1A was found to regulate CD2AP perinuclear localization and levels. In agreement, CD2AP enrichment on endosomes was found more associated with ARPC1A than ARPC1B isoform. Moreover, CD2AP dynamics may be impaired with the downregulation of ARPC1A. ARPC1A loss of function delayed the degradation of APP to the same extent as CD2AP loss of function. Moreover, the loss of function of ARPC1A affects the early endosomes, decreasing EEA1 signal, endosome size, and endosomal APP. In conclusion, our results indicate that CD2AP is recruited to early endosomes by ARP2/3/1A subcomplex dependent-branched F-actin polymerization to stabilize endosomal branched F- actin, which is necessary to mediate APP endosomal sorting for degradation.