α-Synuclein (α-Syn) protein is implicated in the pathogenesis of Parkinson disease (PD). It is primarily cytosolic and interacts with cell membranes. α-Syn also occurs in the nucleus. Here we investigated the mechanisms involved in nuclear translocation of α-Syn. We analyzed alterations in gene expression following induced α-Syn expression in SH-SY5Y cells. Analysis of upstream regulators pointed at alterations in transcription activity of retinoic acid receptors (RARs) and additional nuclear receptors. We show that α-Syn binds RA and translocates to the nucleus to selectively enhance gene transcription. Nuclear translocation of α-Syn is regulated by calreticulin and is leptomycin-B independent. Importantly, nuclear translocation of α-Syn following RA treatment enhances its toxicity in cultured neurons and the expression levels of PD-associated genes, including ATPase cation transporting 13A2 (ATP13A2) and PTEN-induced kinase1 (PINK1). The results link a physiological role for α-Syn in the regulation of RA-mediated gene transcription and its toxicity in the synucleinopathies.

α-Synuclein (α-Syn) is a protein implicated in the pathogenesis of Parkinson's disease (PD). It is an intrinsically disordered protein that binds acidic phospholipids. Growing evidence supports a role for α-Syn in membrane trafficking, including, mechanisms of endocytosis and exocytosis, although the exact role of α-Syn in these mechanisms is currently unclear. Here we investigate the associations of α-Syn with the acidic phosphoinositides (PIPs), phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂) and phosphatidylinositol 3,4-bisphosphate (PI(3,4)P₂). Our results show that α-Syn colocalizes with PIP₂ and the phosphorylated active form of the clathrin adaptor protein 2 (AP2) at clathrin-coated pits. Using endocytosis of transferrin as an indicator for clathrin-mediated endocytosis (CME), we find that α-Syn involvement in endocytosis is specifically mediated through PI(4,5)P₂ levels on the plasma membrane. In accord with their effects on PI(4,5)P₂ levels, the PD associated A30P, E46K, and A53T mutations in α-Syn further enhance CME in neuronal and nonneuronal cells. However, lysine to glutamic acid substitutions at the KTKEGV repeat domain of α-Syn, which interfere with phospholipid binding, are ineffective in enhancing CME. We further show that the rate of synaptic vesicle (SV) endocytosis is differentially affected by the α-Syn mutations and associates with their effects on PI(4,5)P₂ levels, however, with the exception of the A30P mutation. This study provides evidence for a critical involvement of PIPs in α-Syn–mediated membrane trafficking.

A marker for diagnosis of Parkinson’s disease (PD), which reflects on the occurrence of peripheral pathogenic mechanisms, would potentially improve therapy. The significance of α-Synuclein (α-Syn) expression in red blood cells (RBC) is currently unclear. Here we investigated whether RBC’s-expressed α-Syn may associate with PD. To this aim, we determined the levels of total and proteinase K-resistant α-Syn in samples of packed red blood cells (PRBCs). Twenty-one individuals with PD at various disease stages and 15 healthy controls, with similar demographic features, were recruited to this study. α-Syn levels were determined by their biochemical property to bind phospholipids, using a phospholipid-ELISA assay. A significantly lower ratio of total-to-proteinase K-resistant α-Syn levels was detected in PD patients than in the healthy control group. However, there was considerable overlap between the two groups. Suggesting a need for additional markers to be tested in combination with α-Syn levels. To the best of our knowledge, this is the first evidence for an association between RBCs-expressed α-Syn and pathogenic mechanisms involved in PD.

Background: α-Synuclein (α-Syn) is a protein implicated in the pathogenesis of Parkinson’s disease (PD). α-Syn has been shown to associate with membranes and bind acidic phospholipids. However, the physiological importance of these associations to the integrity of axons is not fully clear.Methods: Biochemical, immunohistochemical and ultrastructural analyses in cultured neurons, transgenic mouse brains, PD and control human brains.Results: We analyzed the ultrastructure of cross-sectioned axons localized to white matter tracts (WMTs), within the dorsal striatum of old and symptomatic α-Syn transgenic mouse brains. The analysis indicated a higher density of axons of thinner diameter. Our findings in cultured cortical neurons indicate a role for α-Syn in elongation of the main axon and its collaterals, resulting in enhanced axonal arborization. We show that α-Syn effect to enhance axonal outgrowth is mediated through its activity to regulate membrane levels of the acidic phosphatidylinositol 4,5-bisphosphate (PI4,5P₂). Moreover, our findings link α-Syn- enhanced axonal growth with evidence for axonal injury. In relevance to disease mechanisms, we detect in human brains evidence for a higher degree of corticostriatal glutamatergic plasticity within WMTs at early stages of PD. However, at later PD stages, the respective WMTs in the caudate are degenerated with accumulation of Lewy pathology.Conclusions: Our results show that through regulating PI4,5P₂levels, α-Syn acts to elongate the main axon and collaterals, resulting in a higher density of axons in the striatal WMTs. Based on these results we suggest a role for α-Syn in compensating mechanisms, involving corticostriatal glutamatergic plasticity, taking place early in PD.

Background: Contemporary guidelines recommend the use of sodium-glucose cotransporter 2 inhibitors (SGLT2is) independently of glycemic control in patients with type 2 diabetes and those with kidney disease, with heart failure, or at high risk of cardiovascular disease. Using a large Israeli database, we assessed whether long-term use of SGLT2is versus dipeptidyl peptidase 4 inhibitors (DPP4is) is associated with kidney benefits in patients with type 2 diabetes overall and in those without evidence of cardiovascular or kidney disease. Methods: Patients with type 2 diabetes who initiated SGLT2is or DPP4is between 2015 and 2021 were propensity score-matched (1:1) according to 90 parameters. The kidney-specific composite outcome included confirmed ≥40% decline in eGFR or kidney failure. The kidney-or-death outcome included also all-cause mortality. Risks of outcomes were assessed using Cox proportional hazard regression models. The between-group difference in eGFR slope was also assessed. Analyses were repeated in patients' subgroup lacking evidence of cardiovascular or kidney disease. Results: Overall, 19,648 propensity score-matched patients were included; 10,467 (53%) did not have evidence of cardiovascular or kidney disease. Median follow-up was 38 months (interquartile range, 22–55). The composite kidney-specific outcome occurred at an event rate of 6.9 versus 9.5 events per 1000 patient-years with SGLT2i versus DPP4i. The respective event rates of the kidney-or-death outcome were 17.7 versus 22.1. Compared with DPP4is, initiation of SGLT2is was associated with a lower risk for the kidney-specific (hazard ratio [HR], 0.72; 95% confidence interval [CI], 0.61 to 0.86; P < 0.001) and kidney-or-death (HR, 0.80; 95% CI, 0.71 to 0.89; P < 0.001) outcomes. The respective HRs (95% CI) in those lacking evidence of cardiovascular or kidney disease were 0.67 (0.44 to 1.02) and 0.77 (0.61 to 0.97). Initiation of SGLT2is versus DPP4is was associated with mitigation of the eGFR slope overall and in those lacking evidence of cardiovascular or kidney disease (mean between-group differences 0.49 [95% CI, 0.35 to 0.62] and 0.48 [95% CI, 0.32 to 0.64] ml/min per 1.73 m² per year, respectively). Conclusions: Long-term use of SGLT2is versus DPP4is in a real-world setting was associated with mitigation of eGFR loss in patients with type 2 diabetes, even in those lacking evidence of cardiovascular or kidney disease at baseline.

Sodium–glucose cotransporter-2 (SGLT-2) inhibitors have been shown to reduce hospitalizations for heart failure and to slow progression of kidney damage among patients with type 2 diabetes and pati... Visual Effects of Dapagliflozin on Hospitalizations in Patients With CKD. Sodium–glucose cotransporter-2 (SGLT-2) inhibitors have been shown to reduce hospitalizations for heart failure an... Background: Acute hospitalizations are common in patients with chronic kidney disease (CKD) and often lead to decreases in health-related quality of life and increased care costs. Objective: To det...