α-synuclein (α-Syn) is a presynaptic enriched protein involved in the pathogenesis of Parkinson’s disease. However, the physiological roles of α-Syn remain poorly understood. Recent studies have indicated a critical role of α-Syn in the sensing and generation of membrane curvature during vesicular exocytosis and endocytosis. It has been known to modulate the assembly of SNARE complex during exocytosis including vesicle docking, priming and fusion steps. Growing evidence suggests that α-Syn also plays critical roles in the endocytosis of synaptic vesicles. It also modulates the availability of releasable vesicles by promoting synaptic vesicles clustering. Here, we provide an overview of recent progresses in understanding the function of α-Syn in the regulation of exocytosis, endocytosis, and vesicle recycling under physiological and pathological conditions.

Downy mildew of grapevine (Vitis vinifera L.), caused by the oomycete pathogen Plasmopara viticola, is one of the most serious concerns for grape production worldwide. It has been widely reported that the pathogenesis-related 4 (PR4) protein plays important roles in plant resistance to diseases. However, little is known about the role of PR4 in the defense of grapevine against P. viticola. In this study, we engineered loss-of-function mutations in the VvPR4b gene from the cultivar "Thompson Seedless" using the CRISPR/Cas9 system and evaluated the consequences for downy mildew resistance. Sequencing results showed that deletions were the main type of mutation introduced and that no off-target events occurred. Infection assays using leaf discs showed that, compared to wild-type plants, the VvPR4b knockout lines had increased susceptibility to P. viticola. This was accompanied by reduced accumulation of reactive oxygen species around stomata. Measurement of the relative genomic abundance of P. viticola in VvPR4b knockout lines also demonstrated that the mutants had increased susceptibility to the pathogen. Our results confirm that VvPR4b plays an active role in the defense of grapevine against downy mildew.

The extravasation of leukocytes is a critical step during inflammation which requires the localized opening of the endothelial barrier. This process is initiated by the close interaction of leukocytes with various adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) on the surface of endothelial cells. Here we reveal that mechanical forces generated by leukocyte-induced clustering of ICAM-1 synergistically with fluid shear stress exerted by the flowing blood increase endothelial plasma membrane tension to activate the mechanosensitive cation channel PIEZO1. This leads to increases in [Ca2+]i and activation of downstream signaling events including phosphorylation of SRC, PYK2 and myosin light chain resulting in opening of the endothelial barrier. Mice with endothelium-specific Piezo1 deficiency show decreased leukocyte extravasation in different inflammation models. Thus, leukocytes and the hemodynamic microenvironment synergize to mechanically activate endothelial PIEZO1 and subsequent downstream signaling to initiate leukocyte diapedesis.

Background: Vascular endothelial cells are critical for maintaining blood pressure (BP) by releasing biologically active molecules, such as nitric oxide. A non-endothelial cell resident matricellular protein, COMP (cartilage oligomeric matrix protein), plays a pivotal role in maintaining cardiovascular homeostasis, but little is known about its regulatory effect on BP. Methods: Mice were infused with AngII (angiotensin II; 450 ng/kg per minute) for 3 days via an osmotic minipump, and BP was monitored by a tail-cuff system. Second-order mesenteric arteries were isolated from mice for microvascular tension measurement. Nitric oxide was detected by an electron paramagnetic resonance technique. Small-interfering RNA transfection, co-immunoprecipitation, bioluminescence resonance energy transfer assays, and patch-clamp electrophysiology experiments were used for further detailed mechanism investigation. Results: COMP −/− mice displayed elevated BP and impaired acetylcholine-induced endothelium-dependent relaxation compared with wild-type mice with or without AngII. Inhibition of eNOS (endothelial nitric oxide synthase) abolished the difference in endothelium-dependent relaxation between wild-type and COMP −/− mice. Furthermore, COMP directly interacted with the C-terminus of Piezo1 via its C-terminus and activated the endogenous Piezo1 currents, which induced intracellular Ca 2+ influx, Ca 2+ /calmodulin-dependent protein kinase type II and eNOS activation, and nitric oxide production. The Piezo1 activator, Yoda1, reduced the difference in endothelium-dependent relaxation and BP in wild-type and COMP − /− mice. Moreover, COMP overexpression increased eNOS activation and improved endothelium-dependent relaxation and BP. Conclusions: Our study demonstrated that COMP is a novel Piezo1 regulator that plays a protective role in BP regulation by increasing cellular Ca 2+ influx, eNOS activity, and nitric oxide production.