Acquasaliente, L. | Search bioRxiv

bioRxiv2021

Human -Synuclein Inhibits Platelets Aggregation in vitro by Interfering with the -Thrombin/Protease-Activated Receptor 1 Functional Axis

-Synuclein (Syn) is a small (140 amino acids) disordered, acidic (pI: 4.7) protein, highly conserved in vertebrates and implicated in the pathogenesis of Parkinsons disease (PD), a neurodegenerative disease characterized by the deposition of Syn amyloid fibrils in dopaminergic neurons. Beyond the central nervous system, significant expression of Syn has also been measured in the blood (~1 M), where platelets are the main cellular hosts of Syn. Although the pathological implication of Syn in PD is widely accepted, the physiological role of blood Syn is still elusive. Starting from the notion that platelets are either the major cellular reservoir of Syn in the blood and, concomitantly, act as key players in hemostasis, being activated also by -thrombin (T) via cleavage of protease-activated receptors (PARs), we decided to investigate the possibility that Syn could modulate platelet activation by interfering with the T-PAR functional axis. Using multiple electrode aggregometry, i.e. a fast and specific platelet-function-testing method, as well as steady-state fluorescence spectroscopy, surface plasmon resonance, and fluorescence microscopy, we show here that monomeric Syn functions as a negative regulator of T-mediated platelets activation. Syn acts either directly, via competitive inhibition of PAR1 activation by T and TRAP6 agonist, and indirectly, by scavenging T on the platelet plasma membrane. A simple electrostatic model of Syn platelet antiaggregating effect is proposed and the possible role of the protein at the interplay of amyloidosis and thrombosis is discussed.

biochemistry↗

bioRxiv2020

Mapping specificity, entropy, allosteric changes and substrates in blood proteases by a high-throughput protease screen

Proteases are among the largest protein families in eukaryotic phylae with more than 500 genetically encoded proteases in humans. By cleaving a wide range of target proteins, proteases are critical regulators of a vast number of biochemical processes including apoptosis and blood coagulation. Over the last 20 years, knowledge of proteases has been drastically expanded by the development of proteomic approaches to identify and quantify proteases and their substrates. In spite of their merits, some of these methods are laborious, not scalable or incompatible with native environments. Consequentially, a large number of proteases remain poorly characterized. Here, we introduce a simple proteomic method to profile protease activity based on isolation of protease products from native lysates using a 96FASP filter and their analysis in a mass spectrometer. The method is significantly faster, cheaper, technically less demanding, easily multiplexed and produces accurate protease fingerprints in near-native conditions. By using the blood cascade proteases as a case study we obtained protease substrate profiles of unprecedented depth that can be reliably used to map specificity, entropy and allosteric changes of the protease and to design fluorescent probes and predict physiological substrates. The native protease characterization method is comparable in performance, but largely exceeds the throughput of current alternatives.

biochemistry↗