The impact of physiological crowding on the diffusivity of membrane bound proteins.

Diffusion of transmembrane and peripheral membrane-bound proteins within the crowded cellular membrane environment is essential to diverse biological processes including cellular signaling, endocytosis, and motility. Nonetheless we presently lack a detailed understanding of the influence of physiological levels of crowding on membrane protein diffusion. Utilizing quantitative in vitro measurements, here we demonstrate that the diffusivities of membrane bound proteins follow a single linearly decreasing trend with increasing membrane coverage by proteins. This trend holds for homogenous protein populations across a range of protein sizes and for heterogeneous mixtures of proteins of different sizes, such that protein diffusivity is controlled by the total coverage of the surrounding membrane. These results demonstrate that steric exclusion within the crowded membrane environment can fundamentally limit the diffusive rate of proteins, regardless of their size. In cells this "speed limit" could be modulated by changes in local membrane coverage, providing a mechanism for tuning the rate of molecular interaction and assembly.

AIMP2 restricts EV71 replication by recruiting SMURF2 to promote the degradation of 3D polymerase.

Hand, foot and mouth disease (HFMD), mainly caused by enterovirus 71 (EV71), has frequently occurred in the Asia-Pacific region, posing a significant threat to the health of infants and young children. Therefore, research on the infection mechanism and pathogenicity of enteroviruses is increasingly becoming important. The 3D polymerase, as the most critical RNA-dependent RNA polymerase (RdRp) for EV71 replication, is widely targeted to inhibit EV71 infection. In this study, we identified a novel host protein, AIMP2, capable of binding to 3D polymerase and inhibiting EV71 infection. Subsequent investigations revealed that AIMP2 recruits the E3 ligase SMURF2, which mediates the polyubiquitination and degradation of 3D polymerase. Furthermore, the antiviral effect of AIMP2 extended to the CVA16 and CVB1 serotypes. Our research has uncovered the dynamic regulatory function of AIMP2 during EV71 infection, revealing a novel antiviral mechanism and providing new insights for the development of antienteroviral therapeutic strategies.

Identification of a novel acylthiourea-based potent broad-spectrum inhibitor for enterovirus 3D polymerase in vitro and in vivo.

Enterovirus infections have become a serious public health threat to young children, leading to hand-foot-and-mouth disease and more severe nervous system diseases. Due to the lack of licensed anti enterovirus drugs, we reported herein that a Tenovin-1 analog, acylthiourea-based 4-(tert-butyl)-N-((4-(4-(tert-butyl)benzamido)phenyl)carbamothioyl) benzamide (AcTU), displayed low nanomolar anti-EV-A71 activity with an EC50 of 1.0 nM in RD cells. Moreover, AcTU exhibited nanomolar to picomolar inhibitory activity against a series of enteroviruses including EV-D68, CV-A21, CV-A16 and CV-B1 (EC50 = 0.75-17.15 nM). Mechanistic studies indicated that AcTU inhibited enterovirus proliferation by targeting 3D polymerase. In addition, AcTU displayed moderate pharmacokinetic properties in rats (F = 7.4%, T1/2 = 3.26 h), and in vivo protection studies demonstrated that AcTU orally administered at 0.6 mg/kg/d was highly protective against lethal EV-A71 challenge in mice, potentially reducing mortality from 100% to 20% as well as alleviating symptoms. These results suggested that AcTU could be a potent clinical candidate for the treatment of enterovirus infections.

[Drug delivery of CPC/amifostine/cisplatin complex in vitro and its ability in repairing bone defect and eliminating tumor in vivo].

OBJECTIVE: To investigate the feasibility of using calcium phosphate cement/amifostine/cisplatin complex to fill and repair bone defect, caused by tumor resection. METHODS: Drug concentration in the CPC/ amifostine/cisplatin complex was determined. Rabbits with bone defect and rats with osteosarcoma were implanted with CPC and CPC/amifostine/cisplatin complex. RESULTS: Similar bone growth was observed in the femurs of rabbits implanted with CPC/amifostine/cisplatin complex and those implanted with CPC. CPC/amifostine/cisplatin complex delivered amifostine and cisplatin consistently and eliminated osteosarcoma cells implanted in the rats. CONCLUSION: CPC/amifostine/cisplatin complex repairs bone defect caused by tumors as a filling material.

[In vitro study on physical and chemical properities of calcium phosphate cement/amifostine complex and on vitality of cultured cells].

This study was designed to assess the feasibility of calcium phosphate cement/amifostine complex as a new material for filling the bone defect caused by tumor resection. Mixed-molding method was used, the mass ratios of 0%, 0.1%, 0.5%, 1%, 2% of amifostine/calcium phosphate cement complex being adopted. The curing time, mechanical strength, porosity, scanning electron micrograph, osteosarcoma cells' vitality and vascular endothelial cells' vitality relevant to the complex in vitro were observed. Calcium phosphate cement being loaded with 0.1% and 0.5% amifostine did not affect the curing time, strength, pore size and porosity of calcium phosphate bone cement. In addition proliferation and differentiation of osteosarcoma cells and vascular endothelial cells were not affected. These data suggest that phosphate cement containing 0.1% and 0.5% amifostine be of significance in the treatment regimen as bone defect filling materials..

[Drug delivery of CPC/cisplatin complex in vitro and its ability to repair bone defect and eliminate tumor in vivo].

OBJECTIVE: To explore the best mass ratio of calcium phosphate cement (CPC)/cisplatin complex filling and to repair bone defect caused by tumor resection. METHODS: Mixed-molding method was used to obtain cisplatin/calcium phosphate cement complex at 0, 0.1%, 0.2%, and 0.4% mass ratio. Drug concentration was determined by atomic absorption spectrophotometry. Bone defect of rabbits and osteosarcoma of rats were prepared. We implanted CPC and CPC/cisplatin complex to observe the repair of bone defect and the inhibition of tumor in vivo. RESULTS: CPC containing 0.1% approximately 0.2% cisplatin not only repaired the bone defect in rabbits but also eliminated osteosarcoma in rats. CONCLUSION: CPC containing 0.1% approximately 0.2% cisplatin can repair bone defect and eliminate tumor without influencing the prosthetic precess.

[Physicochemical and sustained drug release properties of calcium phosphate cement/amifostine/cisplatin complex and its effect in repairing bone defect due to tumor resection in rabbits].

OBJECTIVE: To investigate the feasibility of using calcium phosphate cement/amifostine complex as an new filling material for repairing bone defect caused by tumor resection. METHODS: Calcium phosphate cement (CPC)/cisplatin/amifostine complex was prepared at the mass ratio of 1000:2:5. The setting time, mechanical strength, and porosity of the complex were determined, and scanning electron microscopy and assessment of sustained drug release and inhibitory effect against osteosarcoma cells were carried out. The degradation of the material and new bone ingrowth were also observed in a rabbit model of femoral bone defect. RESULTS: The setting time, strength, and porosity, appearances under scanning electron microscope, and sustained drug release properties of CPC/cisplatin/amifostine complex were identical to those of CPC, and the integration of amifostine in the complex did not affect the cytotoxicity of cisplatin against the osteosarcoma cells. Pathological evidences of the degradation of the material and new bone ingrowth into the material were observed with the passage of time following its implantation into the bone defect in rabbits. CONCLUSION: The CPC/cisplatin/amifostine complex can be used as a filling material for repairing bone defect caused by tumor resection and eliminating the residual tumor cells in rabbits.

Generalized coarse-grained model based on point multipole and Gay-Berne potentials.

This paper presents a general coarse-grained molecular mechanics model based on electric point multipole expansion and Gay-Berne [J. Chem. Phys. 74, 3316 (1981)] potential. Coarse graining of van der Waals potential is achieved by treating molecules as soft uniaxial ellipsoids interacting via a generalized anisotropic Gay-Berne function. The charge distribution is represented by point multipole expansion, including point charge, dipole, and quadrupole moments placed at the center of mass. The Gay-Berne and point multipole potentials are combined in the local reference frame defined by the inertial frame of the all-atom counterpart. The coarse-grained model has been applied to rigid-body molecular dynamics simulations of molecular liquids including benzene and methanol. The computational efficiency is improved by several orders of magnitude, while the results are in reasonable agreement with all-atom models and experimental data. We also discuss the implications of using point multipole for polar molecules capable of hydrogen bonding and the applicability of this model to a broad range of molecular systems including highly charged biopolymers.