The platelet glycoprotein Ib-IX-V complex plays critical roles in adhering platelets to sites of blood vessel injury and in platelet aggregation under high fluid shear stress. The complex is composed of four membrane-spanning polypeptides: glycoprotein (GP) Ib␣, GP Ib␤, GP IX, and GP V. Glycoprotein Ib␣ contains a binding site for von Willebrand factor through which it mediates platelet adhesion; GP V is required for the complex to bind thrombin with high affinity; and both GP Ib␤ and GP IX are necessary for efficient plasma membrane expression of the complex. To further define the roles of the individual polypeptide subunits in the biosynthesis and intracellular transport of the GP Ib-IX-V complex, we studied full and partial complexes expressed in heterologous mammalian cells. We found that the full complex was formed within minutes in the endoplasmic reticulum before being transported into the Golgi cisternae. Approximately 160 min were required for the complex to be fully processed and to appear on the plasma membrane. About 25% of GP Ib␣ expressed as part of either a GP Ib-IX complex or a GP Ib-IX-V complex was degraded through a nonlysosomal pathway. Over 60% of GP Ib␣, however, was degraded when it was expressed in partial complexes with only GP Ib␤ or GP IX. The increased degradation was blocked by treating cells either with brefeldin A to prevent the transport of proteins from the endoplasmic reticulum to the Golgi or with lysosomal inhibitors, indicating that GP Ib␣ expressed in partial complexes was targeted to the lysosomes for degradation. These results indicate that the presence of both GP Ib␤ and GP IX, but not the presence of GP V, is required for efficient processing and targeting of GP Ib␣ to the plasma membrane. Absence of either GP Ib␤ or GP IX increased the rate of GP Ib␣ degradation, providing an explanation for why mutation of their genes leads to deficient GP Ib␣ expression and platelet adhesion in Bernard-Soulier syndrome, the deficiency disorder of the complex.When the blood vessel is injured, platelets adhere to the subendothelial matrix exposed at the site of injury. This adhesion is initiated by an interaction between von Willebrand factor exposed on the subendothelium and the glycoprotein (GP)1 Ib-IX-V complex on the platelet surface (1, 2). The same interaction also precipitates pathological platelet aggregation induced by high shear stresses, which occurs at sites of arterial stenosis (3-5).The GP Ib-IX-V complex is composed of four polypeptide subunits, GP Ib␣, GP Ib␤, GP IX, and GP V (1, 6). Glycoprotein Ib␣ is disulfide-linked to GP Ib␤; GP IX and GP V associate with the complex by noncovalent means (7-9). Although the four polypeptides are encoded by different genes (10 -13), they are homologous to each other, all belonging to a phylogenetically widespread protein family defined by the presence of a motif containing tandemly repeated leucine-rich sequences (1,14). Among the four subunits, GP Ib␣ is the largest and so far the only subunit shown to bind von Willebrand factor and...

Protein thermostability can be increased by some glycine to proline mutations in a target protein. However, not all glycine to proline mutations can improve protein thermostability, and this method is suitable only at carefully selected mutation sites that can accommodate structural stabilization. In this study, homology modeling and molecular dynamics simulations were used to select appropriate glycine to proline mutations to improve protein thermostability, and the effect of the selected mutations was proved by the experiments. The structure of methyl parathion hydrolase (MPH) from Ochrobactrum sp. M231 (Ochr‐MPH) was constructed by homology modeling, and molecular dynamics simulations were performed on the modeled structure. A profile of the root mean square fluctuations of Ochr‐MPH was calculated at the nanosecond timescale, and an eight‐amino acid loop region (residues 186–193) was identified as having high conformational fluctuation. The two glycines nearest to this region were selected as mutation targets that might affect protein flexibility in the vicinity. The structures and conformational fluctuations of two single mutants (G194P and G198P) and one double mutant (G194P/G198P) were modeled and analyzed using molecular dynamics simulations. The results predicted that the mutant G194P had the decreased conformational fluctuation in the loop region and might increase the thermostability of Ochr‐MPH. The thermostability and kinetic behavior of the wild‐type and three mutant enzymes were measured. The results were consistent with the computational predictions, and the mutant G194P was found to have higher thermostability than the wild‐type enzyme.

Background: Thrombus formation involves coagulation proteins and platelets. The latter, referred to as platelet-mediated thrombogenesis, is predominant in arterial circulation. Platelet thrombogenesis follows vascular injury when extracellular von Willebrand factor (VWF) binds via its A3 domain to exposed collagen, and the free VWF A1 domain binds to platelet glycoprotein Ib (GPIb). Objectives:To characterize the antiplatelet/antithrombotic activity of the pegylated VWF antagonist aptamer BT200 and identify the aptamer VWF binding site.Methods: BT100 is an optimized aptamer synthesized by solid-phase chemistry and pegylated (BT200) by standard conjugation chemistry. The affinity of BT200 for purified human VWF was evaluated as was VWF inhibition in monkey and human plasma.Efficacy of BT200 was assessed in the monkey FeCl 3 femoral artery thrombosis model. Results: BT200 bound human VWF at an EC 50 of 5.0 nmol/L and inhibited VWF A1 domain activity in monkey and human plasma with mean IC 50 values of 183 and 70 nmol/L. BT200 administration to cynomolgus monkeys caused a time-dependent and dose-dependent effect on VWF A1 domain activity and inhibited platelet function as measured by collagen adenosine diphosphate closure time in the platelet function analyzer. BT200 demonstrated a bioavailability of ≥77% and exhibited a half-life of >100 hours after subcutaneous injection. The treatment effectively prevented arterial occlusion in an FeCl 3 -induced thrombosis model in monkeys. Conclusions: BT200 has shown promising inhibition of human VWF in vitro and prevented arterial occlusion in non-human primates. These data including a long half-life after subcutaneous injections provide a strong rationale for ongoing clinical development of BT200.

Baricitinib therapy in COVID-19: A pilot study on safety and clinical impactDear Editor , 38.1 (37.7-38.7) 0.356 Breath rate N/min, median (IQR), 23 (19.5-24.2) 22 (19.7-24) 0.665 SpO2 (%),median (IQR) 91 (90-92.5) 92 (91.2-93) 0.157 PaO2/FiO2, median (IQR) 290 (199.2-292.2) 268.6 (264.4-295) 0.603 Pulse rate, median (IQR) 82 (73-88.3) 90 (87.2-94.5) 0.069 SBP mm/Hg, median (IQR) 120 (110-131.2) 105 (100-111.25) 0.003 DBP mm/Hg, median (IQR) 70 (60-80) 62.5 (60-66.25) 0.094 WBC (x10 9 /L), median (IQR) 7.8 (5.8-10.8) 8.2 (7.3-8.8) 0.908 Neutrophils (x10 9 /L), median (IQR) 6,5 (4.5-7.7) 6.9 (6.4-7.6) 0.707 Lymphocytes (x10 9 /L), median (IQR) 0.7 (0.7-1.2) 0.89 (0.7-0.9) 1.0 0 0 Hemoglobin (g/L), median (IQR) 118 (102-134.2) 125 (108-134) 0.568 Platelets (x10 9 /L), median (IQR) 203 (174-227) 366 (340-407) 0.0 0 0 ALT (U/L), median (IQR) 28.5 (23.5-52) 44 (37-50) 0.157 AST (U/L), median (IQR) 34 (26.2-48) 44 (34.7-47) 0.525 Creatinine (mg/dl), median (IQR)1.0 (0.9-1.1) 1.00 (0.9-1) 0.583 CRP (mg/dl), median (IQR) 8.2 (5.8-14.5) 3 (1.5-3.2) 0.002 Procalcitonin ng/ml, median (IQR) 0.7 (0.4-1.1) 1.2 (0.8-2.1) 0.902 MEWS, median (IQR) 3 ( 2-3.25) 3 (3-4) 0.544 Abbreviations and symbols: N = number;% = percentage; °C: grade Celsius; min = minute; SpO2 = peripheral capillary oxygen saturation; PaO2/FiO2 = ratio of arterial oxygen partial pressure to fractional inspired oxygen; SBP = systolic blood pressure; DBP = diastolic blood pressure; WBC = white blood cells; AST = serum glutamic oxaloacetic transaminase; ALT = serum alanine aminotransferase; MEWS = Modified Early Warning Score; IQR: Interquartile range.

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Chikungunya fever (CHIKF) is an acute infectious disease that is mediated by the mosquito-transmitted chikungunya virus (CHIKV). People infected with CHIKV may experience high fever, severe joint pain, skin rash, and headache. In recent years, this disease has become a global public health problem. However, there is no licensed vaccine available for CHIKV. Accumulating research data have provided novel approaches and new directions for the development of CHIKV vaccines. Our review focuses on recent progress in CHIKV vaccine studies. The potential vaccine candidates are classified into seven types: inactivated vaccine, subunit vaccine, liveattenuated vaccine, recombinant virus-vectored vaccine, virus-like particle vaccine, chimeric vaccine, and nucleic acid vaccine. These studies will provide important insights into the future development of CHIKV vaccines.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the ongoing coronavirus disease 2019 (COVID-19) pandemic. The S protein is the key viral protein for associating with ACE2, the receptor for SARS-CoV-2. There are many kinds of posttranslational modifications in S protein. However, the detailed mechanism of palmitoylation of SARS-CoV-2 S remains to be elucidated. In our current study, we characterized the palmitoylation of SARS-CoV-2 S. Both the C15 and cytoplasmic tail of SARS-CoV-2 S were palmitoylated. Fatty acid synthase inhibitor C75 and zinc finger DHHC domain-containing palmitoyltransferase (ZDHHC) inhibitor 2-BP reduced the palmitoylation of S. Interestingly, palmitoylation of SARS-CoV-2 S was not required for plasma membrane targeting of S but was critical for S-mediated syncytia formation and SARS-CoV-2 pseudovirus particle entry.

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