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Biomedical subjects

Q Yao

Publications and source records attributed to Q Yao.

At least 19 recordsLinked to original sources
PubMed2005

Reverse cholesterol transport and cholesterol efflux in atherosclerosis.

Reverse cholesterol transport (RCT) is a pathway by which accumulated cholesterol is transported from the vessel wall to the liver for excretion, thus preventing atherosclerosis. Major constituents of RCT include acceptors such as high-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I), and enzymes such as lecithin:cholesterol acyltransferase (LCAT), phospholipid transfer protein (PLTP), hepatic lipase (HL) and cholesterol ester transfer protein (CETP). A critical part of RCT is cholesterol efflux, in which accumulated cholesterol is removed from macrophages in the subintima of the vessel wall by ATP-binding membrane cassette transporter A1 (ABCA1) or by other mechanisms, including passive diffusion, scavenger receptor B1 (SR-B1), caveolins and sterol 27-hydroxylase, and collected by HDL and apoA-I. Esterified cholesterol in the HDL is then delivered to the liver for excretion. In patients with mutated ABCA1 genes, RCT and cholesterol efflux are impaired and atherosclerosis is increased. In studies with transgenic mice, disruption of ABCA1 genes can induce atherosclerosis. Levels of HDL are inversely correlated with incidences of cardiovascular disease. Supplementation with HDL or apoA-I can reverse atherosclerosis by accelerating RCT and cholesterol efflux. On the other hand, pro-inflammatory factors such as interferon-gamma (IFN-gamma), endotoxin, tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1beta), can be atherogenic by impairing RCT and cholesterol efflux, according to in vitro studies. RCT and cholesterol efflux play a major role in anti-atherogenesis, and modification of these processes may provide new therapeutic approaches to cardiovascular disease. Further research on new modifying factors for RCT and cholesterol efflux is warranted.

ATP Binding Cassette Transporter 1↗
PubMed2005

Peroxisome proliferator-activated receptor gamma polymorphisms affect systemic inflammation and survival in end-stage renal disease patients starting renal replacement therapy.

BACKGROUND: Inflammation may contribute to the markedly increased cardiovascular morbidity and mortality in end-stage renal disease (ESRD). However, the prevalence of inflammation varies in different ESRD populations. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is an important nuclear signaling protein that may regulate inflammatory response, and recent studies have revealed genetic polymorphisms that have significant effect on PPAR-gamma signaling. The aim of this study was to clarify whether the PPAR-gamma 161C/T and PPAR-gamma2 Pro12Ala single-nucleotide polymorphisms (SNPs) influence the inter-individual variance of inflammation and mortality in ESRD patients. METHODS: The present prospective study included 229 incident Caucasian ESRD patients (62% males) just prior to starting renal replacement therapy and 207 healthy controls (62% males). Blood samples were taken for measuring systemic inflammatory (CRP, TNF-alpha, IL-6) and nutritional (S-albumin) parameters. The presence of diabetes mellitus, malnutrition (subjective global assessment (SGA)) and cardiovascular disease (CVD) were also assessed. Genotyping of the two PPAR-gamma SNPs was performed using Pyrosequencing. During follow-up (1621+/-63 days), both all-cause and CVD-mortality were investigated. RESULTS: ESRD patients had a higher prevalence of both the PPAR-gamma 161 CC and PPAR-gamma2 Pro12Pro genotypes than the general population (p<0.01). Whereas the Pro12Pro genotype was associated with higher median serum levels of both hs-CRP (p<0.05) and TNF-alpha (p<0.01) the 161CC genotype was associated with a significantly higher (6.6 mg/L versus 3.3 mg/L; p<0.01) median hs-CRP level. Following adjustment for age, gender, SGA and CVD a significantly higher mortality rate was observed in patients with the Pro12Pro genotype. CONCLUSION: This study demonstrates significant differences in PPAR-gamma genotype distribution between ESRD patients and healthy controls. Furthermore, as the PPAR-gamma2 Pro12Pro genotype was associated with both higher levels of biomarkers of inflammation as well as shorter survival, genetic polymorphisms seem to play a role in determining systemic inflammatory status and outcome in this patient group.

Adult↗
PubMed2005

Intravenous delivery of liposome-mediated nonviral DNA is less toxic than intraperitoneal delivery in mice.

Suicide gene therapy has been shown to be an effective means of destroying pancreatic cancer cells. Liposomes have been described as having better efficacy in gene delivery, and an advantage of using liposomes as gene carriers is that they can be used repeatedly in vivo. The objective of this study is to compare the effect of gene delivery routes and to determine whether systemic delivery of the rat insulin promoter (RIP)-directed suicide gene construct would permit cell-specific gene delivery in vivo. Severe combined immunodeficient (SCID) mice were injected with liposome-RIP-TK (thymidine kinase) complex by either the intraperitoneal or the intravenous route. Twenty-four hours post gene delivery, mice received ganciclovir (GCV) treatment twice daily for 14 days. Mice were sacrificed at various time points. Complete necropsy and serum chemistry analysis were performed. Islet morphology was determined using hematoxylin and eosin (H&E) staining. Serum glucose and insulin levels were also determined. To determine the toxic effect on pancreatic islet cells, immunostaining of insulin-producing and glucagon-producing cells was carried out at each time point. H&E staining indicated that both intravenous and intraperitoneal liposome-RIP-TK gene expression had no effect in normal endocrine islet cells. Both gene-delivery routes in mice resulted in normal glycemia and serum insulin levels. The endocrine islets were intact, with a normal distribution pattern of insulin-producing beta cells and glucagon-secreting alpha cells. However, serum chemistry analysis revealed significantly elevated levels of liver enzymes; suggesting that possible liver damage had occurred with the intraperitoneal gene delivery of liposome-pRIP-TK. Intravenous liposome-mediated gene delivery had no effect on liver enzyme levels. Liposome-mediated gene delivery via intravenous injection was less toxic than intraperitoneal delivery. This gene-delivery route requires fewer liposome-DNA complexes and maintains normal liver function. Thus, intravenous delivery of gene therapy would be superior to intraperitoneal administration of gene therapy in mice.

Animals↗
PubMed2005

Human leukemias with mutated FLT3 kinase are synergistically sensitive to FLT3 and Hsp90 inhibitors: the key role of the STAT5 signal transduction pathway.

17-allylamino-17-demethoxygeldanamycin (17-AAG), an inhibitor of the molecular chaperone heat shock protein 90, results in cell type-specific inhibition of proliferation of leukemic cells. GTP14564 is a tyrosine kinase inhibitor actively against FLT3. The current study evaluated the single and combined effects of 17-AAG and GTP14564, and the role of FLT3 in their inhibitory effects. The importance of FLT3 mutations was demonstrated using small interfering RNA (siRNA) targeted to FLT3. Similar to FLT3 siRNA, GTP14564 inhibited FLT3 internal tandem duplication (ITD) cells (MV4;11) and FLT3 amplified wild-type cells (SEMK2-M1), but not wild-type FLT3 cells (RS4;11). However, when RS4;11 cells were stimulated with FLT3-ligand, phosphorylation of STAT5 and GTP14564 inhibition were observed. Responses to GTP14564 in all cell types were directly related to the level of STAT5 phosphorylation in the cells. We observed synergistic effects of combined 17-AAG and GTP14564 in cell lines with FLT3-ITD and amplified wild-type FLT3. Combined treatment with 17-AAG and GTP14564 reduced the levels of p-FLT3 and p-STAT5, enhanced G0/G1 arrest and apoptosis in FLT3-ITD and amplified wild-type FLT3. The combination of 17-AAG with FLT3 kinase inhibitors can enhance targeted therapy in leukemias with FLT3 mutations, such as MLL fusion gene leukemias.

Apoptosis↗
PubMed2005

Properties of pyrolytic chars and activated carbons derived from pilot-scale pyrolysis of used tires.

Used tires were pyrolyzed in a pilot-scale quasi-inert rotary kiln. Influences of variables, such as time, temperature, and agent flow, on the activation of obtained char were subsequently investigated in a laboratory-scale fixed bed. Mesoporous pores are found to be dominant in the pore structures of raw char. Brunauer-Emmett-Teller (BET) surfaces of activated chars increased linearly with carbon burnoff. The carbon burnoff of tire char achieved by carbon dioxide (CO2) under otherwise identical conditions was on average 75% of that achieved by steam, but their BET surfaces are almost the same. The proper activation greatly improved the aqueous adsorption of raw char, especially for small molecular adsorbates, for example, phenol from 6 to 51 mg/g. With increasing burnoff, phenol adsorption exhibited a first-stage linear increase followed by a rapid drop after 30% burnoff. Similarly, iodine adsorption first increased linearly, but it held as the burnoff exceeded 40%, which implied that the reduction of iodine adsorption due to decreasing micropores was partially made up by increasing mesopores. Both raw chars and activated chars showed appreciable adsorption capacity of methylene-blue comparable with that of commercial carbons. Thus, tire-derived activated carbons can be used as an excellent mesoporous adsorbent for larger molecular species.

Adsorption↗
PubMed2005

Effect of small-sized liposomal Adriamycin administered by various routes on a metastatic breast cancer model.

The antitumor effects of small-sized liposomal Adriamycin (LADR) administered by various routes were investigated in rabbits bearing well-developed VX2 tumors in the mammary gland. Rabbits received s.c. or i.v., or s.c. combined with i.v., injections of LADR 6 weeks after tumor implantation. The i.v. route showed a significant inhibitory effect on breast tumors and distant metastases. In comparison, metastases in axillary and mediastinal lymph nodes were more efficiently inhibited after s.c. injection. LADR administered concurrently by both the i.v. and s.c. routes produced satisfactory therapeutic activities on both primary breast tumors and metastases in local-regional lymph nodes, lungs and liver, as shown by slowed growth rates, decreased mRNA expression of proliferating cell nuclear antigen, and extensive necrosis and apoptosis of tumor cells. It is concluded that small-sized LADR administered s.c. provides reliable efficacy on lymphatic metastases of breast cancer and that the addition of treatment by the s.c. route to that by the conventional i.v. route can be recommended as a promising procedure to enhance chemotherapeutic effects in patients with metastatic breast cancer.

Animals↗
PubMed2005

The role of peritoneal dialysis in renal replacement therapy: an update on medical aspects.

In this brief review, we discuss various medical factors that are of importance for the role of peritoneal dialysis (PD) in renal replacement therapy (RRT), whereas the complex role of non medical factors will only be mentioned briefly. The aim of any RRT, including hemodialysis, PD and renal transplantation, is to normalize the volume and composition of the body fluids, to remove uremic toxins, and to improve clinical outcome. In the following, we will focus on adequacy, preservation of residual renal function, fluid balance, infections, nutrition, cardiovascular disease and systemic inflammation in PD as these factors are strong predictors of clinical outcome in end stage renal disease patients.

Humans↗
PubMed2004

Inhibition of the effect of high glucose on the expression of Smad in human peritoneal mesothelial cells.

OBJECTIVE: As high glucose (HG) concentration in peritoneal dialysis (PD) solution is thought to contribute to peritoneal fibrosis, and angiotensin II receptor blockers (ARBs) may have a key role in preventing fibrosis as they may inhibit the TGF-beta1-Smad pathway, the aims of this in vitro study were to investigate 1) if HG affects the expression of Smad in human peritoneal mesothelial cells (HPMCs) and 2) if ARB (losartan) can inhibit this effect METHODS: HPMCs, obtained from non-renal patients undergoing elective abdominal surgery, were stimulated by HG solutions with different concentrations (1.5%, 2.5%, 4.25%) of dextrose and mannitol, and by solutions containing combination with dextrose and losartan. The supernatant was assayed for TGF- beta1 by ELISA and cells were collected for the analysis of Smad family by RT-PCR and Western Blot. RESULTS: 1) HG up-regulated the expression of Smad2 on both gene and protein levels, especially in 2.5% and 4.25% dextrose groups (P<0.05), and also stimulated the expression of Smad4 in 4.25% dextrose group. However, the expression of Smad3 was not affected. 2) High osmolality as such (using mannitol) did not affect the TGF-beta1-Smad signaling pathway. 3) Losartan inhibited the expression of Smad2 on the gene level but not on the protein level. 4) HG up-regulated the level of TGF-beta1 with increasing dextrose concentration, while losartan partially inhibited this effect of HG on releasing of TGF-beta1. CONCLUSION: A high glucose solution up-regulated the expression of Smad2 and Smad4, suggesting that the TGF-beta1-Smad pathway could be involved in the fibrosis of the peritoneum during PD. As losartan inhibited the expression of Smad2 on the gene level and reduced the concentration of TGF-beta1 in our study, the results of this in vitro study suggest that the use of angiotensin II receptor blockers might represent a possible way to prevent and treat peritoneal fibrosis in PD patients. However, further studies in vivo are needed to confirm this hypothesis.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2004

Systemic inflammation in dialysis patients with end-stage renal disease: causes and consequences.

Despite rapid improvements in dialysis technology during the last 20 years, the mortality rate in end-stage renal disease (ESRD) patients treated with dialysis is still unacceptably high and comparable to that of many cancer patients with metastases. The main cause of the increased mortality in ESRD patients is cardiovascular disease (CVD), which is twice as common and advances at twice the rate already in patients with earlier stages of chronic kidney disease as compared to the general population. Although traditional risk factors are common in dialysis patients, they can only in part explain the very high prevalence of CVD in this patient group. Recent evidence demonstrates that chronic inflammation, a non-traditional risk factor which is a commonly observed in dialysis patients, may cause malnutrition and progressive atherosclerotic CVD by several pathogenetic mechanisms. Available data suggest that pro-inflammatory cytokines play a central role in the genesis of both malnutrition and CVD in ESRD. While the long-term effects of chronic inflammation may be most important in the pathogenesis of CVD, the acute-phase reaction may also be a direct cause of acute vascular injury by several pathogenetic mechanisms. The cause(s) of inflammation in dialysis are multifactorial and include both dialysis-related and unrelated factors. Thus, it could be speculated that suppression of the vicious cycle of malnutrition, inflammation, and atherosclerosis (MIA syndrome) would improve survival in dialysis patients. As there are currently no established guidelines for the treatment of chronic inflammation in ESRD patients, studies on the long-term effects of various anti-inflammatory treatment strategies on the nutritional and cardiovascular status as well as outcome in this patient group are warranted.

Humans↗
PubMed2003

A delta-endotoxin encoded in Pseudomonas fluorescens displays a high degree of insecticidal activity.

The short field-life of Bacillus thuringiensis (Bt) insecticidal crystal protein has limited its use. When the Bt toxin is produced in Pseudomonas fluorescens it can be encapsulated and retain its effectiveness for two to three times longer than other Bt formulations. In order to improve Bt expression, we have synthesized cryIA(c) Bt delta-endotoxin encoding region (GenBank AF537267) according to the usage codon of P. fluorescens and transformed the Bt toxin expression cassette into P. fluorescens strains. T7 RNA polymerase and the T7 promoter system were used to control expression of Bt toxin. SDS-PAGE and Western blotting assay revealed that the delta-endotoxin was expressed as 8% of the total protein in P. fluorescens. In in vitro tests, release of toxin from dead bacteria was demonstrated. Supplementation of diets with Bt toxin-containing Pseudomonas bacterium resulted in high mortality of cabbage butterfly ( Pieris brassicae) larvae.

Animals↗
PubMed2003

Somatostatin receptor gene transfer inhibits established pancreatic cancer xenografts.

BACKGROUND: Most human pancreatic adenocarcinoma cells do not express somatostatin receptors, and somatostatin does not inhibit the growth of these cancers. We have demonstrated previously that somatostatin inhibits the growth of pancreatic cancers expressing somatostatin receptor subtype-2 (SSTR2), but not receptor-negative cancers. SSTR2 expression may be an important tumor-suppressor pathway that is lost in human pancreatic cancer. We hypothesized that SSTR2 gene transfer would restore the growth-inhibitory response of human pancreatic cancer to somatostatin. MATERIALS AND METHODS: Palpable human pancreatic adenocarcinoma tumors were established on the backs of nude mice by subcutaneous injection of cultured cells (Panc-1). The animals were divided into 5 groups (n = 10/group). Group I served as an untreated control. Group II received an intramuscular injection of the long-acting somatostatin analogue Sandostatin LAR. Group III received Lac-Z expressing adenovirus via intraperitoneal injection. Group IV received SSTR2 expressing adenovirus via intraperitoneal injection. Group V received SSTR2 expressing adenovirus via intraperitoneal injection and an intramuscular injection of Sandostatin LAR. The rate of tumor growth was assessed with calipers. After 28 days, the animals were anesthetized and exsanguanated, and the tumors were excised and weighed. Plasma somatostatin and octreotide levels were measured by radioimmunoassay. Expression of cell-surface somatostatin-receptor protein and known tumor-suppressor proteins was determined by reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemistry. RESULTS: Systemic delivery of SSTR2-expressing adenovirus by intraperitoneal injection resulted in expression of SSTR2 protein in the subcutaneous human pancreatic cancers. Final tumor weight was significantly decreased in the groups expressing SSTR2 receptors compared to the other 3 groups. Treatment with Sandostatin LAR increased plasma octreotide levels as determined by radioimmunoassay, but had no significant effect on tumor growth. Western blot analysis revealed an up-regulation of the cyclin-dependent kinase inhibitors p27 and p16 in the SSTR2 transfected tumors. CONCLUSIONS: Expression of SSTR2 by human pancreatic cancer causes significant slowing of tumor growth by a mechanism independent of exogenous somatostatin. The mechanism may involve up-regulation of known tumor-suppressor proteins. Restoration of SSTR2 gene expression deserves further study as a potential gene-therapy strategy in human pancreatic cancer.

Adenocarcinoma↗
PubMed2003

Intra-articular adenoviral-mediated gene transfer of trail induces apoptosis of arthritic rabbit synovium.

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that primarily affects joints. In rheumatoid joints there is extensive synovial proliferation with diseased synovium becoming highly aggressive, attaching to the articular cartilage and bone to form what is termed a pannus. The formation of active pannus is central to erosive disease and resulting joint destruction. In this study, we examined the ability to eliminate the hyperplastic synovium by adenoviral-mediated gene transfer of human TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF family that is able to induce apoptosis through interaction with receptors containing death domains, DR4 and DR5. Infection of synovial cells derived from RA patients with Ad.TRAIL resulted in significant apoptosis in three out of five lines. Moreover, primary rabbit synovial fibroblasts were also sensitive to Ad.TRAIL-mediated gene transfer. In a rabbit model of arthritis, intra-articular gene transfer of TRAIL induced apoptosis in cells within the synovial lining, reduced leukocytic infiltration and stimulated new matrix synthesis by cartilage. These results demonstrate that TRAIL can affect the viability of the cells populating the activated synovium in arthritic joints and suggest that the delivery of TRAIL to arthritic joints may represent a non-invasive mechanism for inducing pannus regression.

Adenoviridae↗
PubMed2002

Identification of metastasis-associated genes in early stage non-small cell lung cancer by subtractive hybridization.

Non-small cell lung cancer (NSCLC) is a leading cause of death and a substantial fraction of patients with surgically resected disease ultimately dies due to distant metastasis. To identify gene expression differences in early stage adenocarcinoma that either did or did not metastasize within a 5-year period, we employed a subtractive hybridization strategy of pooled RNA from primary adenocarcinomas (stage I) of the lung. Individual clones (n=225) of the subtracted cDNA library were sequenced. Further analyses of mRNA expression levels in a cohort of 70 NSCLC patients (stage I to IIIA) showed that the metastasis association of the identified genes was stage and histology specific. Cox regression analyses identified two genes (EIF4A1, MALA1) to be independent prognostic parameters for patients' survival in stage I and II disease. These findings could help to identify early-stage NSCLC patients at high risk for the development of distant metastasis.

Biomarkers, Tumor↗
PubMed2001

Rapid assembly of structurally defined and highly functionalized conjugated dienes via tethered enyne metathesis.

[reaction: see text] Conjugated dienes are versatile building blocks in organic synthesis, and the development of new methods for their synthesis remains an important topic in modern synthetic organic chemistry. We describe here an expedient synthesis of highly functionalized conjugated dienes through sequential silicon-tethered ring-closing enyne metathesis mediated by Grubbs' Ru carbene catalysts and Tamao oxidation. Notable attributes of this methodology include short synthetic manipulations and the structural complexity it confers on the resulting diene moiety.

Journal Article↗
PubMed2001

HIV envelope proteins differentially utilize CXCR4 and CCR5 coreceptors for induction of apoptosis.

The involvement of CXCR4 and CCR5 coreceptors in apoptosis induced by the HIV envelope (Env) proteins has not been well defined. We found that simian human immunodeficiency virus (SHIV) virus-like particles (VLPs) containing HIV Env proteins preferentially induce apoptosis of cells corresponding to their coreceptor usage in a CD4+ T cell line. We also demonstrated that induction of apoptosis by SHIV VLPs is correlated with coreceptor usage in a non-T cell line. We examined the effects of SHIV VLPs containing Env proteins derived from either a T-cell-tropic HIV (BH10) strain or a dual-tropic HIV (89.6) strain on induction of apoptosis in recombinant CD4+ human osteosarcoma (HOS) cells expressing either CXCR4 (HOS-CD4.CXCR4) or CCR5 coreceptors (HOS-CD4.CCR5). HOS-CD4.CXCR4 or HOS-CD4.CCR5 cells were activated with concanavalin A and cocultured with VLPs. By TUNEL (TdT-mediated dUTP-X nick end labeling) fluorescence staining and flow cytometry assays, SHIV BH10 VLPs were found to preferentially induce apoptosis in HOS-CD4.CXCR4 cells but not in HOS-CD4 or HOS-CD4.CCR5 cells. On the other hand, SHIV 89.6 VLPs induced an elevated level of apoptosis in both HOS-CD4.CXCR4 and HOS-CD4.CCR5 cells in a dose-dependent fashion. These data demonstrate that T-cell-tropic BH10 Env preferentially utilizes CXCR4, but not CCR5, for induction of apoptosis, whereas dual-tropic 89.6 Env induces apoptosis in both CXCR4- and CCR5-containing cell lines.

Apoptosis↗
PubMed2001

Oligomeric interactions between phospholamban molecules regulate Ca-ATPase activity in functionally reconstituted membranes.

Phospholamban (PLB) is a major target of the beta-adrenergic cascade in the heart, and functions as an endogenous inhibitor of Ca-ATPase transport activity. To identify whether oligomeric interactions between PLB molecules are involved in regulating Ca-ATPase transport activity, we have investigated functional interactions between PLB and the Ca-ATPase in proteoliposomes of purified PLB functionally co-reconstituted with the SERCA2a isoform of the Ca-ATPase isolated from cardiac sarcoplasmic reticulum (SR). The calcium sensitivity of this reconstituted preparation and functional stimulation by cAMP-dependent protein kinase (PKA) are virtually identical to those of the Ca-ATPase in cardiac SR microsomes, ensuring the functional relevance of this reconstituted preparation. Interactions between PLB molecules were measured following covalent modification of the single lysine (i.e., Lys(3)) in PLB isolated from cardiac SR membranes with fluorescein isothiocyanate (FITC) prior to co-reconstitution with the Ca-ATPase. FITC modification of PLB does not interfere with the ability of PLB to inhibit the Ca-ATPase, since FITC-PLB co-reconstituted with the Ca-ATPase exhibits a similar calcium dependence of Ca-ATPase activation to that observed in native SR membranes. Thus, the functional arrangement of PLB with the Ca-ATPase is not modified by FITC modification. Using changes in the anisotropy of FITC-PLB resulting from fluorescence resonance energy transfer (FRET) between proximal PLB molecules to measure the average size and spatial arrangement of FITC chromophores, we find that PLB self-associates to form oligomers whose spatial arrangement with respect to one another is in agreement with earlier suggestions that PLB exists predominantly as a homopentamer. The inability of PKA to activate PLB following covalent modification with FITC permits functional interactions between PLB molecules associated with the Ca-ATPase activation to be identified. A second-order loss of Ca-ATPase activation by PKA is observed as a function of the fractional contribution of FITC-PLB, indicating that PKA-dependent activation of two PLB molecules within a quaternary complex containing the Ca-ATPase is necessary for activation of the Ca-ATPase. We suggest that the requirement for activation of two PLB molecules by PKA represents a physiological mechanism to ensure that activation of the Ca-ATPase following beta-adrenergic stimulation in the heart only occurs above a threshold level of PKA activation.

Animals↗
PubMed2001

Three membrane-proximal amino acids in the human parainfluenza type 2 (HPIV 2) F protein are critical for fusogenic activity.

In this study, we investigated the role of the membrane-proximal region of the human parainfluenza virus type 2 (HPIV2) F protein by mutational analysis, including deletion, insertion, and substitution. Deletion or replacement of the entire 12 amino acid region (aa 474-485) of the HPIV2 F protein completely abolished its fusion activity when coexpressed with the HPIV2 HN protein. Deletion of groups of four of aa 478-485, single alanine, or other amino acid substitutions among aa 478-485 had minimal or limited effects on HPIV2 F/HN-induced cell fusion. However, a significant reduction in, or complete inhibition of, fusion activity was observed when aa 474-477 were deleted, or the N475, F476, or F477 residues were singly substituted with alanine. In addition, insertions of four amino acids at this region or deletion of eight or more amino acids significantly reduced F protein fusion activity. The oligomerization patterns and levels of cell surface expression of the mutant F proteins were compared to those of the wild-type HPIV2 F protein. The mutant HPIV2 F proteins defective in fusion were also found to be unable to initiate hemifusion, indicating that there is a specific requirement for three specific amino acids as well as the spacing in this region for initiating lipid mixing.

Amino Acids↗