Fever Promotes T Lymphocyte Trafficking via a Thermal Sensory Pathway Involving Heat Shock Protein 90 and α4 Integrins.

Fever is an evolutionarily conserved response that confers survival benefits during infection. However, the underlying mechanism remains obscure. Here, we report that fever promoted T lymphocyte trafficking through heat shock protein 90 (Hsp90)-induced α4 integrin activation and signaling in T cells. By inducing selective binding of Hsp90 to α4 integrins, but not ß2 integrins, fever increased α4-integrin-mediated T cell adhesion and transmigration. Mechanistically, Hsp90 bound to the α4 tail and activated α4 integrins via inside-out signaling. Moreover, the N and C termini of one Hsp90 molecule simultaneously bound to two α4 tails, leading to dimerization and clustering of α4 integrins on the cell membrane and subsequent activation of the FAK-RhoA pathway. Abolishment of Hsp90-α4 interaction inhibited fever-induced T cell trafficking to draining lymph nodes and impaired the clearance of bacterial infection. Our findings identify the Hsp90-α4-integrin axis as a thermal sensory pathway that promotes T lymphocyte trafficking and enhances immune surveillance during infection.

GIT/PIX Condensates Are Modular and Ideal for Distinct Compartmentalized Cell Signaling.

Enzymes or enzyme complexes can be concentrated in different cellular loci to modulate distinct functional processes in response to specific signals. How cells condense and compartmentalize enzyme complexes for spatiotemporally distinct cellular events is not well understood. Here we discover that specific and tight association of GIT1 and ß-Pix, a pair of GTPase regulatory enzymes, leads to phase separation of the complex without additional scaffolding molecules. GIT1/ß-Pix condensates are modular in nature and can be positioned at distinct cellular compartments, such as neuronal synapses, focal adhesions, and cell-cell junctions, by upstream adaptors. Guided by the structure of the GIT/PIX complex, we specifically probed the role of phase separation of the enzyme complex in cell migration and synapse formation. Our study suggests that formation of modular enzyme complex condensates via phase separation can dynamically concentrate limited quantities of enzymes to distinct cellular compartments for specific and optimal signaling.

Structural basis of ligand binding modes at the neuropeptide Y Y1 receptor.

Neuropeptide Y (NPY) receptors belong to the G-protein-coupled receptor superfamily and have important roles in food intake, anxiety and cancer biology 1,2 . The NPY-Y receptor system has emerged as one of the most complex networks with three peptide ligands (NPY, peptide YY and pancreatic polypeptide) binding to four receptors in most mammals, namely the Y1, Y2, Y4 and Y5 receptors, with different affinity and selectivity 3 . NPY is the most powerful stimulant of food intake and this effect is primarily mediated by the Y1 receptor (Y1R) 4 . A number of peptides and small-molecule compounds have been characterized as Y1R antagonists and have shown clinical potential in the treatment of obesity 4 , tumour 1 and bone loss 5 . However, their clinical usage has been hampered by low potency and selectivity, poor brain penetration ability or lack of oral bioavailability 6 . Here we report crystal structures of the human Y1R bound to the two selective antagonists UR-MK299 and BMS-193885 at 2.7 and 3.0 Å resolution, respectively. The structures combined with mutagenesis studies reveal the binding modes of Y1R to several structurally diverse antagonists and the determinants of ligand selectivity. The Y1R structure and molecular docking of the endogenous agonist NPY, together with nuclear magnetic resonance, photo-crosslinking and functional studies, provide insights into the binding behaviour of the agonist and for the first time, to our knowledge, determine the interaction of its N terminus with the receptor. These insights into Y1R can enable structure-based drug discovery that targets NPY receptors.

The association of sickle cell disorder with adverse outcomes in COVID-19 patients: A meta-analysis.

The aim is to elucidate the relationship between sickle cell disorder and severe COVID-19. We systematically searched the required articles in three electronic databases, extracting and pooling effect sizes (ES) and 95% confidence interval (CI) from each eligible study to evaluate the effect of combined sickle cell disorder on adverse consequences in patients with COVID-19. This meta-analysis included 21 studies. Sickle cell disease (SCD) was a risk factor for mortality (pooled ES = 1.70, 95% CI: 1.00-2.92, p = 0.001), hospitalization (pooled ES = 6.21, 95% CI: 3.60-10.70, p = 0.000) and intensive care unit (ICU) admission (pooled ES = 2.29, 95% CI: 1.61-3.24, p = 0.099) in COVID-19 patients. Patients with SCD had an increased risk of respiratory failure/mechanical ventilation, but a statistical association was not found (pooled ES = 1.21, 95%CI: 0.74-1.98, p = 0.036). There was significant heterogeneity between SCD and death, hospitalization, and respiratory failure/mechanical ventilation. The results of meta-regression of SCD and hospitalization suggested that the tested variables including Area (p = 0.642), study design (p = 0.739), sample size (p = 0.397), proportion of males (p = 0.708), effect type (p = 0.723), whether confounding factors are adjusted (p = 0.606) might not be the source of heterogeneity. In addition, sickle cell trait (SCT) was significantly associated with the mortality (pooled ES = 1.54, 95% CI: 1.28-1.85, p = 0.771) and hospitalization (pooled ES = 1.20, 95% CI: 1.07-1.35，p = 0.519) in patients with COVID-19. But any increased risk of ICU admission/severe (pooled ES = 1.24, 95% CI: 0.95-1.62, p = 0.520) and mechanical ventilation (OR = 1.00, 95%CI:0.59-1.69) in COVID-19 patients with SCT was not observed. Sensitivity analysis demonstrated that the results were robust. The results of the funnel plot and Egger's test did not support the existence of publication bias. Current meta-analysis indicated that sickle cell disorder has a meaningful impact on COVID-19 progression to severe cases and associated deaths. However, further investigations and research to validate the current findings is indispensable.

Relationship between Helicobacter pylori and Incident Hypertension as well as Blood Pressure: A Systematic Review and Meta-Analysis.

BACKGROUND: Helicobacter pylori (H. pylori) may be a risk factor for hypertension, but the reported studies have given conflicting results. This study aimed to explore the association between H. pylori infection and hypertension risk and blood pressure. METHOD: PubMed, Embase, Web of Science, CNKI, Weipu, and Wanfang databases were searched for articles published up to June 2, 2021. Dual-selection and data abstraction were conducted. Random-effect models were used to measure pooled estimates. All data were analyzed with Stata 14.0 SE (StataCorp, College Station, TX, USA). RESULTS: A total of 55 studies with 198,750 individuals were included in the meta-analysis. Among them, 33 studies reported the relationship between H. pylori infection and the risk of hypertension, and 25 studies reported the association of H. pylori infection with systolic blood pressure (SBP) and diastolic blood pressure (DBP). Three studies reported both of the above. Meta-analysis showed that H. pylori infection increased the risk of hypertension by 32% (odd ratio: 1.32, 95% CI: 1.15-1.52). Compared with non-H. pylori-infection individuals, the subjects with H. pylori infection had elevated levels of SBP (WMD: 1.86, 95% CI: 1.21-2.50) and DBP (WMD: 1.12, 95% CI: 0.81-1.43). CONCLUSION: This meta-analysis suggested that H. pylori infection increased the risk of hypertension. This may provide a new strategy for hypertension prevention. However, the association between H. pylori infection and hypertension needs to be confirmed in further prospective cohort studies.

Oral membrane-biomimetic nanoparticles for enhanced endocytosis and regulation of tumor-associated macrophage.

Enterocyte uptake with high binding efficiency and minor endogenous interference remains a challenge in oral nanocarrier delivery. Enterocyte membrane-biomimetic lipids may universally cooperate with endogenous phosphatidyl choline via a biorthogonal group. In this study, we developed a sophorolipid-associated membrane-biomimetic choline phosphate-poly(lactic-co-glycolic) acid hybrid nanoparticle (SDPN). Aided by physical stability in the gastrointestinal tract and rapid mucus diffusion provided by association with sophorolipid, these nanoparticles show improved endocytosis, driven by dipalmitoyl choline phosphate-phosphatidyl choline interaction as well as its optimized membrane fluidity and rigidity. Luteolin- and silibinin-co-loaded with SDPN alleviated breast cancer metastasis in 4T1 tumor-bearing mice by regulating the conversion of tumor-associated M2 macrophages into the M1 phenotype and reducing the proportion of the M2-phenotype through co-action on STAT3 and HIF-1α. In addition, SDPN reduces angiogenesis and regulates the matrix barrier in the tumor microenvironment. In conclusion, this membrane-biomimetic strategy is promising for improving the enterocyte uptake of oral SDPN and shows potential to alleviate breast cancer metastasis.

A meta-analysis of the association between Helicobacter pylori infection and risk of hepatic encephalopathy.

BACKGROUND: Although the association between Helicobacter pylori (H. pylori) infection and hepatic encephalopathy (HE) has been confirmed through some research, the results of these relevant studies still remain controversial. We conducted an updated meta-analysis based on published studies to address this issue. METHODS: A systematic search was conducted, reviewing all studies about the association between H. pylori infection and HE, through November 2021. The outcome measures were presented as odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: In total, 13 studies provided data from 2784 subjects. H. pylori infection increased the risk of HE by 32% (OR = 2.32, 95% CI: 1.78-3.04). The effect became greater after hepatic encephalopathy was divided into overt HE and minimal hepatic encephalopathy (MHE) (HE OR = 2.66, 95% CI: 2.01-3.51, MHE OR = 1.74, 95% CI: 1.10-2.76). After H. pylori eradication, the risk of HE was reduced by 64%. CONCLUSIONS: H. pylori infection is significantly associated with HE, and the infection rate of H. pylori also increases with the severity of HE. Eradication of H. pylori has a protective effect on HE. Therefore, it is necessary to eradicate H. pylori in HE treatments.

[Effects of Platycodonis Radix-Curcumae Rhizoma on oral nanoparticle uptake and in vitro inhibition against breast cancer metastasis].

This study combined the herbal pair Platycodonis Radix-Curcumae Rhizoma(PR-CR) possessing an inhibitory effect on tumor cell proliferation and metastasis with the active component of traditional Chinese medicine(TCM) silibinin-loaded nanoparticles(NPs) with a regulatory effect on tumor microenvironment based on the joint effect on tumor cells and tumor microenvironment to inhi-bit cell metastasis. The effects of PR-CR on the cellular uptake of NPs and in vitro inhibition against breast cancer proliferation and metastasis were investigated to provide an experimental basis for improving nanoparticle absorption and enhancing therapeutic effects. Silibinin-loaded lipid-polymer nanoparticles(LPNs) were prepared by the nanoprecipitation method and characterized by transmission electron microscopy. The NPs were spherical or quasi-spherical in shape with obvious core-shell structure. The mean particle size was 107.4 nm, Zeta potential was-27.53 mV. The cellular uptake assay was performed by in vitro Caco-2/E12 coculture cell model and confocal laser scanning microscopy(CLSM), and the results indicated that PR-CR could promote the uptake of NPs. Further, in situ intestinal absorption assay by the CLSM vertical scanning approach showed that PR-CR could promote the absorption of NPs in the enterocytes of mice. The inhibitory effect of NPs on the proliferation and migration of 4T1 cells was analyzed using 4T1 breast cancer cells and co-cultured 4T1/WML2 cells, respectively. The results of the CCK8 assay showed that PR-CR-containing NPs could enhance the inhibition against the proliferation of 4T1 breast cancer cells. The wound healing assay indicated that PR-CR-containing NPs enhanced the inhibition against the migration of 4T1 breast cancer cells. This study enriches the research on oral absorption of TCM NPs and also provides a new idea for utilizing the advantages of TCM to inhibit breast cancer metastasis.

The CRISPR-Cas system as a tool for diagnosing and treating infectious diseases.

Emerging and relapsing infectious diseases pose a huge health threat to human health and a new challenge to global public health. Rapid, sensitive and simple diagnostic tools are keys to successful management of infectious patients and containment of disease transmission. In recent years, international research on Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-related proteins (Cas) has revolutionized our understanding of biology. The CRISPR-Cas system has the advantages of high specificity, high sensitivity, simple, rapid, low cost, and has begun to be used for molecular diagnosis and treatment of infectious diseases. In this paper, we described the biological principles, application fields and prospects of CRISPR-Cas system in the molecular diagnosis and treatment of infectious diseases, and compared it with existing molecular diagnosis methods, the advantages and disadvantages were summarized.

Phase Separation of MAGI2-Mediated Complex Underlies Formation of Slit Diaphragm Complex in Glomerular Filtration Barrier.

BACKGROUND: Slit diaphragm is a specialized adhesion junction between the opposing podocytes, establishing the final filtration barrier to urinary protein loss. At the cytoplasmic insertion site of each slit diaphragm there is an electron-dense and protein-rich cellular compartment that is essential for slit diaphragm integrity and signal transduction. Mutations in genes that encode components of this membrane-less compartment have been associated with glomerular diseases. However, the molecular mechanism governing formation of compartmentalized slit diaphragm assembly remains elusive. METHODS: We systematically investigated the interactions between key components at slit diaphragm, such as MAGI2, Dendrin, and CD2AP, through a combination of biochemical, biophysical, and cell biologic approaches. RESULTS: We demonstrated that MAGI2, a unique MAGUK family scaffold protein at slit diaphragm, can autonomously undergo liquid-liquid phase separation. Multivalent interactions among the MAGI2-Dendrin-CD2AP complex drive the formation of the highly dense slit diaphragm condensates at physiologic conditions. The reconstituted slit diaphragm condensates can effectively recruit Nephrin. A nephrotic syndrome-associated mutation of MAGI2 interfered with formation of the slit diaphragm condensates, thus leading to impaired enrichment of Nephrin. CONCLUSIONS: Key components at slit diaphragm (e.g., MAGI2 and its complex) can spontaneously undergo phase separation. The reconstituted slit diaphragm condensates can be enriched in adhesion molecules and cytoskeletal adaptor proteins. Therefore, the electron-dense slit diaphragm assembly might form via phase separation of core components of the slit diaphragm in podocytes.

Differential Expression of α-Enolase in Clinical Gastric Tissues and Cultured Normal/Cancer Cells in Response to Helicobacter pylori Infection and cagA Transfection.

Background and Objectives: The role of α-enolase (ENO1) in Helicobacter pylori-related gastric lesions might be a critical factor in the pathogenesis, but remains undefined. Materials and Methods: This study investigated the differential expression of α-enolase in clinical gastric specimens and cultured normal/cancer cells in response to H. pylori (cagA+) infection and cagA transfection using qPCR, Western blots and histochemical methods. Results: A total of 172 gastric specimens were collected from 142 patients, the former comprising chronic superficial gastritis (CSG), precancerous diseases (PCDs, including atrophic gastritis, intestinal metaplasia and dysplasia) and gastric cancer (GC) cases. Among the CSG and PCD cases, the H. pylori-infected group had significantly elevated ENO1 mRNA levels compared with the uninfected group. In the GC cases, differential ENO1 expressions were detected between the cancer tissues and the paracancerous tissues. Notably, significant difference was first detected between the GC cell (AGS) and the normal cell (GES-1) as a response of ENO1 to H. pylori infection and cagA transfection. Conclusions: This report reveals that ENO1 expression is associated with H. pylori infection, cagA transfection, co-culture duration, multiplicity of infection, gastric normal/cancerous cell lines and cellular differentiation. The findings may be crucial bases for further ascertaining H. pylori pathogenic mechanism and formulating novel therapeutic and diagnostic strategies.

Structural analysis of the STING adaptor protein reveals a hydrophobic dimer interface and mode of cyclic di-GMP binding.

STING is an essential signaling molecule for DNA and cyclic di-GMP (c-di-GMP)-mediated type I interferon (IFN) production via TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) pathway. It contains an N-terminal transmembrane region and a cytosolic C-terminal domain (CTD). Here, we describe crystal structures of STING CTD alone and complexed with c-di-GMP in a unique binding mode. The strictly conserved aa 153-173 region was shown to be cytosolic and participated in dimerization via hydrophobic interactions. The STING CTD functions as a dimer and the dimerization was independent of posttranslational modifications. Binding of c-di-GMP enhanced interaction of a shorter construct of STING CTD (residues 139-344) with TBK1. This suggests an extra TBK1 binding site, other than serine 358. This study provides a glimpse into the unique architecture of STING and sheds light on the mechanism of c-di-GMP-mediated TBK1 signaling.

The crystal structure of ORP3 reveals the conservative PI4P binding pattern.

Oxysterol-binding protein (OSBP) and its related protein (ORP) constitute a conserved family of lipid transfer proteins (LTPs). ORPs have been implicated as intracellular lipid exchanger and sensor in recent years, which regulate the lipid homeostasis and signal pathway. OSBP-related protein 3 plays key role in controlling cell adhesion and migration and could be developed as the drug target for cancer therapy. Here, we report the crystal structures of human ORP3 ORD to 2.1 Å and ORD-PI4P complex to 3.2 Å. The binding assay in vitro confirms the ORP3 has the capability of PI4P binding. This study further verifies that the PI4P is the common ligand of all ORPs and ORPs should be the lipid exchanger in membrane contact sites(MCS).

Riboflavin Is Directly Involved in N-Dealkylation Catalyzed by Bacterial Cytochrome P450 Monooxygenases.

Like a vast number of enzymes in nature, bacterial cytochrome P450 monooxygenases require an activated form of flavin as a cofactor for catalytic activity. Riboflavin is the precursor of FAD and FMN that serves as indispensable cofactor for flavoenzymes. In contrast to previous notions, herein we describe the identification of an electron-transfer process that is directly mediated by riboflavin for N-dealkylation by bacterial P450 monooxygenases. The electron relay from NADPH to riboflavin and then via activated oxygen to heme was proposed based on a combination of X-ray crystallography, molecular modeling and molecular dynamics simulation, site-directed mutagenesis and biochemical analysis of representative bacterial P450 monooxygenases. This study provides new insights into the electron transfer mechanism in bacterial P450 enzyme catalysis and likely in yeasts, fungi, plants and mammals.

A meta-analysis of the association between Helicobacter pylori infection and risk of atherosclerotic cardiovascular disease.

BACKGROUND: Helicobacter pylori (H pylori) infection may be a risk factor for cardiovascular disease (CVD), but the reported researches have given conflicting results. AIMS: To investigate the association between H pylori infection and risk of atherosclerotic CVD. MATERIALS AND METHODS: The studies were retrieved in Embase, PubMed, Web of Science (published from Jan 1, 1990, to Jan 31, 2020, language restrictions: English). All studies included used data from case-control studies and cohort studies of cardiovascular adverse events. Random effect models were used to measure pooled estimates. All data were analyzed with Stata 11.2 SE (StataCorp, College Station, TX). RESULTS: Helicobacter pylori infection increased the risk of adverse cardiovascular events by 51% (40 studies, n = 19 691, odd ratio [OR] = 1.51, 95% confidence interval [CI]: 1.34-1.70). The effect was greater for studies that the type of CVDs was myocardial infarction (MI) and cerebrovascular disease (MI OR = 1.80, 95% CI: 1.42-2.26, cerebrovascular disease OR = 1.54, 95% CI: 1.27-1.89). Meanwhile, CagA seropositive H pylori strains were associated with a significantly increased risk of cardiovascular adverse events based on published research data (OR = 1.73, 95% CI: 1.40-2.14). CONCLUSION: In conclusion, H pylori infection enhanced the risk of atherosclerotic cardiovascular adverse events, especially in some patients with MI and cerebrovascular disease. This study will provide guidance for the targeted prevention and treatment of CVDs. But this association need to be confirmed by more prospective studies.

Structures of phlebovirus glycoprotein Gn and identification of a neutralizing antibody epitope.

Severe fever with thrombocytopenia syndrome virus (SFTSV) and Rift Valley fever virus (RVFV) are two arthropod-borne phleboviruses in the Bunyaviridae family, which cause severe illness in humans and animals. Glycoprotein N (Gn) is one of the envelope proteins on the virus surface and is a major antigenic component. Despite its importance for virus entry and fusion, the molecular features of the phleboviruse Gn were unknown. Here, we present the crystal structures of the Gn head domain from both SFTSV and RVFV, which display a similar compact triangular shape overall, while the three subdomains (domains I, II, and III) making up the Gn head display different arrangements. Ten cysteines in the Gn stem region are conserved among phleboviruses, four of which are responsible for Gn dimerization, as revealed in this study, and they are highly conserved for all members in Bunyaviridae Therefore, we propose an anchoring mode on the viral surface. The complex structure of the SFTSV Gn head and human neutralizing antibody MAb 4-5 reveals that helices α6 in subdomain III is the key component for neutralization. Importantly, the structure indicates that domain III is an ideal region recognized by specific neutralizing antibodies, while domain II is probably recognized by broadly neutralizing antibodies. Collectively, Gn is a desirable vaccine target, and our data provide a molecular basis for the rational design of vaccines against the diseases caused by phleboviruses and a model for bunyavirus Gn embedding on the viral surface.

Prognostic Significance of ADAM17 for Gastric Cancer Survival: A Meta-Analysis.

Background and objectives: The prognostic role of a disintegrin and metalloproteinase (ADAM) 17 has been widely assessed in gastric cancer. However, the results are inconsistent. We performed a meta-analysis to evaluate the prognostic significance of ADAM17 and its association with clinicopathological parameters. Methods: The databases of PubMed, Web of Science, and Embase were searched for relevant articles published up to April 2020. The reported hazard ratios (HRs) and odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were pooled to evaluate the strength of the association. Stata 12.1 was used to perform statistical analyses. Results: Seven studies, including 1757 patients, were screened for the meta-analysis. Compared with the high ADAM17 expression group, the pooled HR was higher in the low ADAM17 expression group (HR = 2.04, 95% CI 1.66-2.50; I2 = 18.1%; p = 0.299). High ADAM17 expression was also related to the tumor node metastasis (TNM) stages (OR = 4.09, 95% CI 1.85-9.04; I2 = 84.1%; p = 0.000), lymph node metastasis (OR = 3.08, 95% CI 1.13-8.36; I2 = 79.7%; p = 0.007), and ages (OR = 1.65, 95% CI 1.24-2.21; I2 = 0%; p = 0.692) of the gastric patients. Conclusions: This meta-analysis revealed that ADAM17 is a significant biomarker for poor prognosis in gastric cancer.

Structural analyses of key features in the KANK1·KIF21A complex yield mechanistic insights into the cross-talk between microtubules and the cell cortex.

The cross-talk between dynamic microtubules and the cell cortex plays important roles in cell division, polarity, and migration. A critical adaptor that links the plus ends of microtubules with the cell cortex is the KANK N-terminal motif and ankyrin repeat domains 1 (KANK1)/kinesin family member 21A (KIF21A) complex. Genetic defects in these two proteins are associated with various cancers and developmental diseases, such as congenital fibrosis of the extraocular muscles type 1. However, the molecular mechanism governing the KANK1/KIF21A interaction and the role of the conserved ankyrin (ANK) repeats in this interaction are still unclear. In this study, we present the crystal structure of the KANK1·KIF21A complex at 2.1 Å resolution. The structure, together with biochemical studies, revealed that a five-helix-bundle-capping domain immediately preceding the ANK repeats of KANK1 forms a structural and functional supramodule with its ANK repeats in binding to an evolutionarily conserved peptide located in the middle of KIF21A. We also show that several missense mutations present in cancer patients are located at the interface of the KANK1·KIF21A complex and destabilize its formation. In conclusion, our study elucidates the molecular basis underlying the KANK1/KIF21A interaction and also provides possible mechanistic explanations for the diseases caused by mutations in KANK1 and KIF21A.

A non-canonical role of the p97 complex in RIG-I antiviral signaling.

RIG-I is a well-studied sensor of viral RNA that plays a key role in innate immunity. p97 regulates a variety of cellular events such as protein quality control, membrane reassembly, DNA repair, and the cell cycle. Here, we report a new role for p97 with Npl4-Ufd1 as its cofactor in reducing antiviral innate immune responses by facilitating proteasomal degradation of RIG-I. The p97 complex is able to directly bind both non-ubiquitinated RIG-I and the E3 ligase RNF125, promoting K48-linked ubiquitination of RIG-I at residue K181. Viral infection significantly strengthens the interaction between RIG-I and the p97 complex by a conformational change of RIG-I that exposes the CARDs and through K63-linked ubiquitination of these CARDs. Disruption of the p97 complex enhances RIG-I antiviral signaling. Consistently, administration of compounds targeting p97 ATPase activity was shown to inhibit viral replication and protect mice from vesicular stomatitis virus (VSV) infection. Overall, our study uncovered a previously unrecognized role for the p97 complex in protein ubiquitination and revealed the p97 complex as a potential drug target in antiviral therapy.

Characterization by high-resolution crystal structure analysis of a triple-helix region of human collagen type III with potent cell adhesion activity.

Collagen is one of the most abundant and important proteins in the human body. Human collagen type III (hCOL3A1) belongs to the fibril-forming collagens and is widely distributed in extensible connective tissue like skin, internal organs, or the vascular system. It plays key roles in wound healing, collagen fibrillogenesis, and normal cardiovascular development in human. The charged residues are considered to be an important characteristic of hCOL3A1, especially for collagen binding and recognition. Here we found that a triple helix fragment of hCOL3A1, Gly489-Gly510, contained multiple charged residues, as well as representative Glu-Lys-Gly and Glu-Arg-Gly charged triplets. We solved the crystal structure of this new fragment to a high-resolution of 1.50 Šand identified some important conformations of this new triple-helix region, including strong hydrogen bonds in interchain and interhelical interactions in addition to obvious flexible bending for the triple helix. We also found that the synthetic collagen peptides around this region exhibited potent activities through integrin-mediated peptide-membrane interaction. We then developed a method to produce a recombinant protein consisting of 16 tandem repeats of the triple-helix fragment of hCOL3A1 with strong activity without cytotoxicity. These results provide a strong base for further functional studies of human collagen type III and the method developed in this study can be applied to produce hCOL3A1-derived proteins or other tandem-repeat proteins with membrane adhesion activity.