Amyloid aggregates accumulate in melanoma metastasis modulating YAP activity

Abstract

Melanoma progression is generally associated with increased transcriptional activity mediated by the Yes‐associated protein (YAP). Mechanical signals from the extracellular matrix are sensed by YAP, which then activates the expression of proliferative genes, promoting melanoma progression and drug resistance. Which extracellular signals induce mechanotransduction, and how this is mediated, is not completely understood. Here, using secretome analyses, we reveal the extracellular accumulation of amyloidogenic proteins, i.e. premelanosome protein (PMEL), in metastatic melanoma, together with proteins that assist amyloid maturation into fibrils. We also confirm the accumulation of amyloid‐like aggregates, similar to those detected in Alzheimer disease, in metastatic cell lines, as well as in human melanoma biopsies. Mechanistically, beta‐secretase 2 (BACE2) regulates the maturation of these aggregates, which in turn induce YAP activity. We also demonstrate that recombinant PMEL fibrils are sufficient to induce mechanotransduction, triggering YAP signaling. Finally, we demonstrate that BACE inhibition affects cell proliferation and increases drug sensitivity, highlighting the importance of amyloids for melanoma survival, and the use of beta‐secretase inhibitors as potential therapeutic approach for metastatic melanoma.

Secret3D Workflow for Secretome Analysis

“…For each cycle, one full MS1 scan range = 300–1,650 m/z ( Figure 2 ), was followed by 12 MS2 scans using an isolation window of 2.0 m/z. MS analysis is performed as reported in Matafora et al., 2020 . Raw MS files are processed with MaxQuant software, making use of the Andromeda search engine ( Cox et al., 2011 ).…”

“…MS analysis is performed as reported in Matafora et al., 2020 . Raw MS files are processed with MaxQuant software, making use of the Andromeda search engine ( Cox et al., 2011 ).…”

“…With the Secret3D workflow, the MS analysis of the digested proteins usually leads to the identification of roughly 2,000 proteins. We have analyzed more than ten different cell lines and the number of proteins identified is comparable ( Matafora et al., 2020 ).…”

“…It allows efficient and robust protein identification and quantitation and provides information on putative N-glycosylation sites of the secreted proteins. For complete details on the use and execution of this protocol, please refer to Matafora et al. (2020) .…”

“…For complete details on the use and execution of this protocol, please refer to Matafora et al. (2020) .…”