α-Synuclein plays a major role in Parkinson disease. Unraveling the mechanisms of α-synuclein aggregation is essential to understand the formation of Lewy bodies and their involvement in dopaminergic cell death. α-Synuclein is ubiquitylated in Lewy bodies, but the role of α-synuclein ubiquitylation has been mysterious. We now report that the ubiquitin-protein isopeptide ligase seven in absentia homolog (SIAH) directly interacts with and monoubiquitylates α-synuclein and promotes its aggregation in vitro and in vivo, which is toxic to cells. Mass spectrometry analysis demonstrates that SIAH monoubiquitylates α-synuclein at lysines 12, 21, and 23, which were previously shown to be ubiquitylated in Lewy bodies. SIAH ubiquitylates lysines 10, 34, 43, and 96 as well. Suppression of SIAH expression by short hairpin RNA to SIAH-1 and SIAH-2 abolished α-synuclein monoubiquitylation in dopaminergic cells, indicating that endogenous SIAH ubiquitylates α-synuclein. Moreover, SIAH co-immunoprecipitated with α-synuclein from brain extracts. Inhibition of proteasomal, lysosomal, and autophagic pathways, as well as overexpression of a ubiquitin mutant less prone to deubiquitylation, G76A, increased monoubiquitylation of α-synuclein by SIAH. Monoubiquitylation increased the aggregation of α-synuclein in vitro. At the electron microscopy level, monoubiquitylated α-synuclein promoted the formation of massive amounts of amorphous aggregates. Monoubiquitylation also increased α-synuclein aggregation in vivo as observed by increased formation of α-synuclein inclusion bodies within dopaminergic cells. These inclusions are toxic to cells, and their formation was prevented when endogenous SIAH expression was suppressed. Our data suggest that monoubiquitylation represents a possible trigger event for α-synuclein aggregation and Lewy body formation.

Background: Subterranean blind mole rats(Spalax)are hypoxia tolerant (down to 3% O₂), long lived (>20 years) rodents showing no clear signs of aging or aging related disorders. In 50 years ofSpalaxresearch, spontaneous tumors have never been recorded among thousands of individuals.Here we addressed the questions of (1) whetherSpalaxis resistant to chemically-induced tumorigenesis, and (2) whether normal fibroblasts isolated fromSpalaxpossess tumor-suppressive activity.Results: Treating animals with 3-Methylcholantrene (3MCA) and 7,12-Dimethylbenz(a) anthracene/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA), two potent carcinogens, confirmedSpalaxhigh resistance to chemically induced cancers. While all mice and rats developed the expected tumors following treatment with both carcinogens, amongSpalaxno tumors were observed after DMBA/TPA treatment, while 3MCA induced benign fibroblastic proliferation in 2Spalaxindividuals out of12, and only a single animal from the advanced age group developed malignancy 18 months post-treatment. The remaining animals are still healthy 30 months post-treatment.In vitroexperiments showed an extraordinary ability of normalSpalaxcultured fibroblasts to restrict malignant behavior in a broad spectrum of human-derived and in newly isolatedSpalax3MCA-induced cancer cell lines. Growth of cancer cells was inhibited by either direct interaction withSpalaxfibroblasts or with soluble factors released into culture media and soft agar. This was accompanied by decreased cancer cell viability, reduced colony formation in soft agar, disturbed cell cycle progression, chromatin condensation and mitochondrial fragmentation. Cells from another cancer resistant subterranean mammal, the naked mole rat, were also tested for direct effect on cancer cells and, similar toSpalax, demonstrated anti-cancer activity. No effect on cancer cells was observed using fibroblasts from mouse, rat orAcomys.Spalaxfibroblast conditioned media had no effect on proliferation of noncancerous cells.Conclusions: This report provides pioneering evidence thatSpalaxis not only resistant to spontaneous cancer but also to experimentally induced cancer, and shows the unique ability ofSpalaxnormal fibroblasts to inhibit growth and kill cancer cells, but not normal cells, either through direct fibroblast-cancer cell interaction or via soluble factors. Obviously, along with adaptation to hypoxia,Spalaxhas evolved efficient anti-cancer mechanisms yet to be elucidated. Exploring the molecular mechanisms allowingSpalaxto survive in extreme environments and to escape cancer as well as to kill homologous and heterologous cancer cells may hold the key for understanding the molecular nature of host resistance to cancer and identify new anti-cancer strategies for treating humans.

Telomere dynamics have been found to be better predictors of survival and mortality than chronological age. Telomeres, the caps that protect the end of linear chromosomes, are known to shorten with age, inducing cell senescence and aging. Furthermore, differences in age-related telomere attrition were established between short-lived and long-lived organisms. However, whether telomere length is a “biological thermometer” that reflects the biological state at a certain point in life or a biomarker that can influence biological conditions, delay senescence and promote longevity is still an ongoing debate. We cross-sectionally tested telomere length in different tissues of two long-lived (naked mole-rat and Spalax) and two short-lived (rat and mice) species to tease out this enigma. While blood telomere length of the naked mole-rat (NMR) did not shorten with age but rather showed a mild elongation, telomere length in three tissues tested in the Spalax declined with age, just like in short-lived rodents. These findings in the NMR, suggest an age buffering mechanism, while in Spalax tissues the shortening of the telomeres are in spite of its extreme longevity traits. Therefore, using long-lived species as models for understanding the role of telomeres in longevity is of great importance since they may encompass mechanisms that postpone aging.

A multikinase inhibitor of the Raf/mitogen‐activated protein kinase kinase (MEK)/extracellular signal‐regulated kinase (ERK) pathway, sorafenib, is increasingly being used in the management of hepatocellular carcinoma, and its combination with conventional chemotherapeutics has stimulated particular interest. Although the combination of sorafenib with doxorubicin (DOX) is presently being investigated in a phase III randomized trial, little is known about the molecular mechanisms of their interaction. Because DOX causes cell death through upregulation of the MEK/ERK pathway, and sorafenib has an opposite influence on the same cascade, we hypothesized that co‐treatment with these drugs may lead to an antagonistic effect. DOX treatment arrested proliferation and induced autophagic cell death in Hep3B cells, whereas apoptotic changes were not conspicuous. Sorafenib alone affected viability and caused massive mitochondrial degradation. However, when added together with DOX, sorafenib facilitated cell cycle progression, increased survival, and reduced autophagy. To evaluate the molecular mechanisms of this phenomenon, we examined the expression of ERK1/2, protein kinase B (Akt), and cyclin D1, as well as the members of Bcl‐2 family. ERK1/2 activation induced by DOX was suppressed by sorafenib. Similarly, ERK targeting with the selective inhibitor U0126 impaired DOX‐induced toxicity. Treatment with sorafenib, either alone or in combination with DOX, resulted in Akt activation. The role of sorafenib‐induced degradation of cyclin D1 in the suppression of DOX efficiency is discussed. In conclusion, MEK/ERK counteraction, stimulation of survival via Akt and dysregulation of cyclin D1 could contribute to the escape from DOX‐induced autophagy and thus promote cancer cell survival. The use of MEK/ERK inhibitors in combination with chemotherapeutics, intended to enhance anticancer efficacy, requires the consideration of possible antagonistic effects.