The role of alpha-synuclein in nucleolar DNA double-strand break repair and cellular senescence

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PROJECT SUMMARY Genomic stability is very closely linked to diseases associated with aging, like neurodegeneration and cancer. Interestingly, strong evidence suggests unexpected links between these two diseases, since epidemiological studies have found that Parkinson’s Disease (PD) patients are at an increased risk of developing melanoma. Furthermore, this relationship is bidirectional; individuals diagnosed with melanoma are at an increased risk of developing PD. Although these clinical associations are well-established, the cellular and molecular pathways linking these diseases are poorly understood. PD is the second most common neurodegenerative disease associated with a complex combination of genetic and environmental risk factors, which manifests into devastating movement and coordination deficits. Its hallmark pathological finding is the presence of aggregated forms of alpha-synuclein (αSyn) in the substantia nigra of patient brains. Recent studies have also found a previously unrecognized role for αSyn in melanomagenesis and metastasis, highlighting the role of αSyn in regions outside of the central nervous system. Several studies have shown that melanoma cells overexpress αSyn and that this is important for promoting cell proliferation and growth; however, the underlying role of αSyn within melanogenesis is unknown. We have previously demonstrated that αSyn is important in DNA double- strand break (DSB) repair, and my new studies show an important role for αSyn within the nucleolus. Furthermore, genomic instability within the nucleolus has been associated with several diseases linked to cellular aging and has been shown to induce cellular senescence. Therefore, based on my preliminary data and these published findings, I hypothesize that the upregulation of αSyn plays a critical role in cells to facilitate nucleolar DSB repair, limit senescence, and thus contribute to overall cell survival. This hypothesis will be tested through two aims: first, I will determine the role of αSyn in nucleolar DSB repair (Aim 1) and next, determine the role of αSyn in cellular senescence inhibition and melanoma growth and metastatic potential (Aim 2). I will accomplish these goals through both in vitro and in vivo methodology. Using a human melanoma cell line that highly expresses αSyn, SK-Mel28, I will investigate the localization and function of αSyn in the nucleolus using various imaging and proteomic techniques. I will knockout αSyn to investigate loss-of-function nucleolar phenotypes and whether cellular senescence inhibition is altered. I will then reintroduce not only wildtype αSyn, but also four neurodegeneration-associated variants. To test whether αSyn plays a role in melanoma growth and metastasis through nucleolar DSB and senescence inhibition in vivo, I will breed an αSyn KO spontaneous melanoma mouse model. Through histological examination I will determine whether αSyn loss-of-function impairs nucleolar DSB repair and senescence inhibition, delays primary tumor growth, and diminishes metastasis. Achieving these goals will have a profound impact on the aging field by introducing genomic instability and cellular senescence concepts to our understanding of the cross-talk between PD and melanoma.