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Tetraspanins, such as CD81, can form lateral associations with each other and with other transmembrane proteins. These interactions may underlie CD81 functions in multiple cellular processes, such as adhesion, morphology, migration, and differentiation. Since CD81's role in neuronal cells' migration has not been established, we here evaluated effects of CD81 on the migratory phenotype of SH-SY5Y neuroblastoma cells. CD81 was found enriched at SH-SY5Y cell's membrane, co-localizing with its interactor filamentous-actin (F-actin) in migratory relevant structures of the leading edge (filopodia, stress fibers, and adhesion sites). CD81 overexpression increased the number of cells with a migratory phenotype, in a potentially phosphatidylinositol 3 kinase (PI3K)-Ak strain transforming (AKT) mediated manner. Indeed, CD81 also co-localized with AKT, a CD81-interactor and actin remodeling agent, at the inner leaflet of the plasma membrane. Pharmacologic inhibition of PI3K, the canonical AKT activator, led both to a decrease in the acquisition of a migratory phenotype and to a redistribution of intracellular CD81 and F-actin into cytoplasmic agglomerates. These findings suggest that in neuronal-like cells CD81 bridges active AKT and actin, promoting the actin remodeling that leads to a motile cell morphology. Further studies on this CD81-mediated mechanism will improve our knowledge on important physiological and pathological processes such as cell migration and differentiation, and tumor metastasis. ; This work was supported by Fundação para a Ciência e Tecnologia (Portuguese Ministry of Science and Technology), Centro 2020 and Portugal2020, the COMPETE program, QREN, and the European Union (FEDER program) via the Institute for Biomedicine iBiMED UID/BIM/ 04501/2013, fellowship SFRH/BD/90996/2012, project PTDC/CVT-CVT/ 32261/2017, and the support of the LiM facility of iBiMED, a member of the Portuguese Platform of BioImaging (PPBI- POCI-01-0145-FEDER-022122). ; published

Reversing protein aggregation within cells may be an important tool to fight protein-misfolding disorders such as Alzheimer's, Parkinson's, and cardiovascular diseases. Here we report the design and synthesis of a family of steroid−quinoline hybrid compounds based on the framework combination approach. This set of hybrid compounds effectively inhibited Aβ1−42 self-aggregation in vitro by delaying the exponential growth phase and/or reducing the quantity of fibrils in the steady state. Their disaggregation efficacy was further demonstrated against preaggregated Aβ1−42 peptides in cellular assays upon their endocytosis by neuroblastoma cells, as they reverted both the number and the average area of fibrils back to basal levels. The antiaggregation effect of these hybrids was further tested and demonstrated in a cellular model of general protein aggregation expressing a protein aggregation fluorescent sensor. Together, our results show that the new cholesterol−quinoline hybrids possess wide and marked disaggregation capacities and are therefore promising templates for the development of new drugs to deal with conformational disorders. ; Thanks are due to the University of Aveiro, FCT/MEC, Centro 2020 and Portugal2020, the COMPETE Program, and the European Union (FEDER Program) via the financial support to the research units LAQV-REQUIMTE (UIDB/50006/2020), IBiMED (UID/BIM/04501/2019) and CICECO- Aveiro Institute of Materials (UID/CTM/50011/2019), financed by national funds through the FCT/MCTES, to the Portuguese NMR Network, to the ThiMES Project (POCI-01- 0145-FEDER-016630), and to the PAGE Project "Protein Aggregation Across the Lifespan" (CENTRO-01-0145- FEDER-000003), including postdoctoral grants to H.M.T.A. (BPD/UI98/4861/2017) and R.N.d.S. (BPD/UI98/6327/2018). M.P. was supported by Ph.D. Grant SFRH/BD/135655/2018. A.R.S. and S.G. were supported by national funds (OE) through FCT, I.P., in the scope of the framework contract foreseen in numbers 4, 5, and 6 of Article 23 of the Decree-Law 57/2016 of August ...