Structural Insight into IAPP-Derived Amyloid Inhibitors and Their Mechanism of Action.

Designed peptides derived from the islet amyloid polypeptide (IAPP) cross-amyloid interaction surface with Aß (termed interaction surface mimics or ISMs) have been shown to be highly potent inhibitors of Aß amyloid self-assembly. However, the molecular mechanism of their function is not well understood. Using solution-state and solid-state NMR spectroscopy in combination with ensemble-averaged dynamics simulations and other biophysical methods including TEM, fluorescence spectroscopy and microscopy, and DLS, we characterize ISM structural preferences and interactions. We find that the ISM peptide R3-GI is highly dynamic, can adopt a ß-like structure, and oligomerizes into colloid-like assemblies in a process that is reminiscent of liquid-liquid phase separation (LLPS). Our results suggest that such assemblies yield multivalent surfaces for interactions with Aß40. Sequestration of substrates into these colloid-like structures provides a mechanistic basis for ISM function and the design of novel potent anti-amyloid molecules.

Key aromatic/hydrophobic amino acids controlling a cross-amyloid peptide interaction versus amyloid self-assembly.

The interaction of the intrinsically disordered polypeptide islet amyloid polypeptide (IAPP), which is associated with type 2 diabetes (T2D), with the Alzheimer's disease amyloid-ß (Aß) peptide modulates their self-assembly into amyloid fibrils and may link the pathogeneses of these two cell-degenerative diseases. However, the molecular determinants of this interaction remain elusive. Using a systematic alanine scan approach, fluorescence spectroscopy, and other biophysical methods, including heterocomplex pulldown assays, far-UV CD spectroscopy, the thioflavin T binding assay, transmission EM, and molecular dynamics simulations, here we identified single aromatic/hydrophobic residues within the amyloid core IAPP region as hot spots or key residues of its cross-interaction with Aß40(42) peptide. Importantly, we also find that none of these residues in isolation plays a key role in IAPP self-assembly, whereas simultaneous substitution of four aromatic/hydrophobic residues with Ala dramatically impairs both IAPP self-assembly and hetero-assembly with Aß40(42). Furthermore, our experiments yielded several novel IAPP analogs, whose sequences are highly similar to that of IAPP but have distinct amyloid self- or cross-interaction potentials. The identified similarities and major differences controlling IAPP cross-peptide interaction with Aß40(42) versus its amyloid self-assembly offer a molecular basis for understanding the underlying mechanisms. We propose that these insights will aid in designing intervention strategies and novel IAPP analogs for the management of type 2 diabetes, Alzheimer's disease, or other diseases related to IAPP dysfunction or cross-amyloid interactions.

A Hot-Segment-Based Approach for the Design of Cross-Amyloid Interaction Surface Mimics as Inhibitors of Amyloid Self-Assembly.

The design of inhibitors of protein-protein interactions mediating amyloid self-assembly is a major challenge mainly due to the dynamic nature of the involved structures and interfaces. Interactions of amyloidogenic polypeptides with other proteins are important modulators of self-assembly. Here we present a hot-segment-linking approach to design a series of mimics of the IAPP cross-amyloid interaction surface with Aß (ISMs) as nanomolar inhibitors of amyloidogenesis and cytotoxicity of Aß, IAPP, or both polypeptides. The nature of the linker determines ISM structure and inhibitory function including both potency and target selectivity. Importantly, ISMs effectively suppress both self- and cross-seeded IAPP self-assembly. Our results provide a novel class of highly potent peptide leads for targeting protein aggregation in Alzheimer's disease, type 2 diabetes, or both diseases and a chemical approach to inhibit amyloid self-assembly and pathogenic interactions of other proteins as well.

Role of microRNA-21 in regulating 3T3-L1 adipocyte differentiation and adiponectin expression.

MicroRNAs are endogenous small RNAs with a high degree of conservation, participating in a variety of vital activities. In present study, to explore the effect of microRNAs on 3T3-L1 adipocyte differentiation and adiponectin expression, the adipo-related microRNAs were screened and identified by micorRNA microarray. The highly expression plasmid of microRNA-21 with obvious expression up-regulation (miR-21) and its anti-sense (miR-21 inhibitor) were constructed and transfected into 3T3-L1 preadipocytes. The effect of miR-21 on 3T3-L1 adipocyte differentiation was observed, and the protein and mRNA expression level of adiponectin and AP-1 were analyzed. Results showed that, the expression profiles of microRNAs significantly changed during 3T3-L1 adipocyte differentiation. The expression of miR-21 was obviously up-regulated. miR-21 could significantly promote adipocyte differentiation, increase adiponectin mRNA and protein expression, while decrease AP-1 protein level. Meanwhil, miR-21 inhibitor blocked the effects of miR-21 mentioned above. The overexpression of AP-1 could absolutely reverse the stimulatory effect of miR-21 on adiponectin. miR-21 plays an important role in regulating adipocyte differentiation and adiponectin expression by inhibiting AP-1 expression.

Dissecting the role of single regions of an IAPP mimic and IAPP in inhibition of Aß40 amyloid formation and cytotoxicity.

Alzheimer's disease (AD) and type 2 diabetes (T2D) are linked to the self-association of ß-amyloid peptide (Aß) and islet amyloid polypeptide (IAPP), respectively. We have shown that IAPP-GI, a soluble IAPP analogue and mimic of nonamyloidogenic and nontoxic IAPP, binds Aß with high affinity and blocks its cytotoxic self-assembly and fibrillogenesis. We have also shown that IAPP and Aß interact with each other into nonfibrillar and nontoxic heterocomplexes that suppress cytotoxic self-association by both polypeptides. The Aß-IAPP interaction might thus be a molecular link between AD and T2D. We studied the role of individual IAPP-GI and IAPP regions in their inhibitory function on Aß40 self-association and cytotoxicity. We found that the presence of the two hot-spot regions of the Aß-IAPP interaction interface in IAPP(8-28) is not sufficient for inhibitory function and that, in addition to IAPP(8-28), the presence of the N-terminal region IAPP(1-7) is absolutely required. By contrast, the C-terminal region, IAPP(30-37), is not required although its presence together with IAPP(1-7) in IAPP-GI results in a marked enhancement of the inhibitory effect as compared to IAPP(1-28)-GI. We suggest that the inhibitory effect of IAPP-GI and IAPP on Aß40 fibrillogenesis and cell toxicity is mediated primarily by interactions involving the hot regions of the Aß-IAPP interaction interface and the N terminus of IAPP while a concerted and likely structure-stabilizing action of the N- and C-terminal IAPP regions potentiates this effect. These results identify important molecular determinants of the amyloid suppressing function of the Aß40-IAPP interaction and could contribute to the design of novel inhibitors of Aß40 aggregation and cell degeneration.

[Effect of Lewis y antigen on regulating gene expression of partial drug resistance associated proteins in human ovarian cancer cell line RMG-I-H].

OBJECTIVE: To investigate the influence of Lewis y antigen on the gene expression of partial drug resistance associated proteins in human ovarian cancer cell line RMG-I-H. METHODS: RT-PCR was used to determine the gene expressions of partial drug resistance associated proteins in RMG-I-H cell line transfected with alpha1, 2-fucosyltransferases gene and RMG-I cell line, as well as in RMG-I-H treated with or without anti-Lewis y monoclonal antibody at the concentration of 10 micro/g/ml. The immunocytochemical method was used to detect the expression of P-glycoprotein (P-gp) in RMG-I and RMG-I-H cell lines. RMG-I and RMG-I-H cells were transplanted into nude mice and the expression of P-gp in the tissues was measured by immunohistochemistry. RESULTS: The mRNA expressions of protein kinase C-alpha (PKC-alpha), topoismerase I ( Topo I ), multidrug resistance-associated protein-1 (MRP-1), and MRP-2 were significantly higher in RMG-I-H cells than those in RMG-I cells (0.46 +/- 0.02 vs. 0.27 +/- 0.05, 0.82 +/- 0.08 vs. 0.52 +/- 0.04, 0.66 +/- 0.07 vs. 0.34 +/- 0.12, and 0.44 +/- 0.08 vs. 0.23 +/- 0.05; all P < 0.05). However, the mRNA expression of multi-drug resistance 1 (MDR-1) was significantly lower in RMG-I-H cells than that in RMG-I cells (0.26 +/- 0.05 vs. 0.45 +/- 0.08, P < 0.05). The P-gp level increased in RMG-I-H cells compared with that in RMG-I cells both in vivo and in vitro (P < 0.05). Expressions of MDR-1, MRP-1, MRP-2, PKC-alpha, and Topo I mRNA decreased by the time in RMG-I-H cells treated with anti-Lewis y monoclonal antibody (all P < 0.05), while mRNA expressions of those genes in the control group did not statistically change (P > 0.05). In addition, MDR-1, MRP-1, MRP-2, PKC-alpha, and Topo I mRNA expressions were significantly lower in RMG-I-H cells treated with anti-Lewis y monoclonal antibody than those in the control group at 6 hours (all P < 0.05) and the inhibition ratios were 48.55%, 77.50%, 70.18%, 45.86%, and 46.13%, respectively. CONCLUSION: The Lewis y antigen of the human ovarian cancer cell surface is closely correlated with the regulation on the gene expression of partial drug resistance associated proteins.

Bi-frontal pneumocephalus is an independent risk factor for early postoperative agitation in adult patients admitted to intensive care unit after elective craniotomy for brain tumor: A prospective cohort study.

Postoperative agitation frequently occurs after general anesthesia and may be associated with serious consequences. However, studies in neurosurgical patients have been inadequate. We aimed to investigate the incidence and risk factors for early postoperative agitation in patients after craniotomy, specifically focusing on the association between postoperative pneumocephalus and agitation. Adult intensive care unit admitted patients after elective craniotomy under general anesthesia were consecutively enrolled. Patients were assessed using the Sedation-Agitation Scale during the first 24 hours after operation. The patients were divided into two groups based on their maximal Sedation-Agitation Scale: the agitation (Sedation-Agitation Scale ≥ 5) and non-agitation groups (Sedation-Agitation Scale ≤ 4). Preoperative baseline data, intraoperative and intensive care unit admission data were recorded and analyzed. Each patient's computed tomography scan obtained within six hours after operation was retrospectively reviewed. Modified Rankin Scale and hospital length of stay after the surgery were also collected. Of the 400 enrolled patients, agitation occurred in 13.0% (95% confidential interval: 9.7-16.3%). Body mass index, total intravenous anesthesia, intraoperative fluid intake, intraoperative bleeding and transfusion, consciousness after operation, endotracheal intubation kept at intensive care unit admission and mechanical ventilation, hyperglycemia without a history of diabetes, self-reported pain and postoperative bi-frontal pneumocephalus were used to build a multivariable model. Bi-frontal pneumocephalus and delayed extubation after the operation were identified as independent risk factors for postoperative agitation. After adjustment for confounding, postoperative agitation was independently associated with worse neurologic outcome (odd ratio: 5.4, 95% confidential interval: 1.1-28.9, P = 0.048). Our results showed that early postoperative agitation was prevalent among post-craniotomy patients and was associated with adverse outcomes. Improvements in clinical strategies relevant to bi-frontal pneumocephalus should be considered. TRIAL REGISTRATION: ClinicalTrials.gov (NCT02318199).

Inhibition of hIAPP amyloid-fibril formation and apoptotic cell death by a designed hIAPP amyloid- core-containing hexapeptide.

The pathogenesis of type II diabetes is associated with the aggregation of the 37-residue human islet amyloid polypeptide (hIAPP) into cytotoxic beta sheet aggregates and fibrils. We have recently shown that introduction of two N-methyl rests in the beta sheet- and amyloid-core-containing sequence hIAPP(22-27), or NFGAIL converted this amyloidogenic and cytotoxic sequence into nonamyloidogenic and noncytotoxic NF(N-Me)GA(N-Me)IL. Here, we show that NF(N-Me)GA(N-Me)IL is able to bind with high-affinity full-length hIAPP and to inhibit its fibrillogenesis. NF(N-Me)GA(N-Me)IL also inhibits hIAPP-mediated apoptotic beta cell death. By contrast, unmodified NFGAIL does not inhibit hIAPP amyloidogenesis and cytotoxicity, suggesting that N-methylation conferred on NFGAIL the properties of NF(N-Me)GA(N-Me)IL. These results support the concept that rational N-methylation of hIAPP amyloid-core sequences may be a valuable strategy to design pancreatic-amyloid diagnostics and therapeutics for type II diabetes.

Lung-protective Ventilation in Patients with Brain Injury: A Multicenter Cross-sectional Study and Questionnaire Survey in China.

BACKGROUND: Over the years, the mechanical ventilation (MV) strategy has changed worldwide. The aim of the present study was to describe the ventilation practices, particularly lung-protective ventilation (LPV), among brain-injured patients in China. METHODS: This study was a multicenter, 1-day, cross-sectional study in 47 Intensive Care Units (ICUs) across China. Mechanically ventilated patients (18 years and older) with brain injury in a participating ICU during the time of the study, including traumatic brain injury, stroke, postoperation with intracranial tumor, hypoxic-ischemic encephalopathy, intracranial infection, and idiopathic epilepsy, were enrolled. Demographic data, primary diagnoses, indications for MV, MV modes and settings, and prognoses on the 60th day were collected. Multivariable logistic analysis was used to assess factors that might affect the use of LPV. RESULTS: A total of 104 patients were enrolled in the present study, 87 (83.7%) of whom were identified with severe brain injury based on a Glasgow Coma Scale ≤8 points. Synchronized intermittent mandatory ventilation (SIMV) was the most frequent ventilator mode, accounting for 46.2% of the entire cohort. The median tidal volume was set to 8.0 ml/kg (interquartile range [IQR], 7.0-8.9 ml/kg) of the predicted body weight; 50 (48.1%) patients received LPV. The median positive end-expiratory pressure (PEEP) was set to 5 cmH2O (IQR, 5-6 cmH2O). No PEEP values were higher than 10 cmH2O. Compared with partially mandatory ventilation, supportive and spontaneous ventilation practices were associated with LPV. There were no significant differences in mortality and MV duration between patients subjected to LPV and those were not. CONCLUSIONS: Among brain-injured patients in China, SIMV was the most frequent ventilation mode. Nearly one-half of the brain-injured patients received LPV. Patients under supportive and spontaneous ventilation were more likely to receive LPV. TRIAL REGISTRATION: ClinicalTrials.org NCT02517073 https://clinicaltrials.gov/ct2/show/NCT02517073.

Emergence agitation during recovery from intracranial surgery under general anaesthesia: a protocol and statistical analysis plan for a prospective multicentre cohort study.

INTRODUCTION: Emergence agitation after intracranial surgery is an important clinical issue during anaesthesia recovery. The aim of this multicentre cohort study is to investigate the incidence of emergence agitation, identify the risk factors and determine clinical outcomes in adult patients after intracranial surgery under general anaesthesia. Additionally, we will deliberately clarify the relationship between postoperative pneumocephalus and agitation. METHODS AND ANALYSIS: The present study is a prospective multicentre cohort study. Five intensive care units (ICUs) in China will participate in the study. Consecutive adult patients admitted to the ICUs after intracranial surgery will be enrolled. Sedation-Agitation Scale (SAS) or Richmond Agitation-Sedation Scale (RASS) will be used to evaluate the patients 12 h after the enrolment. Agitation is defined as an SAS score of 5-7, or an RASS score of +2 to +4. According to the maximal SAS and RASS score, patients will be divided into two cohorts: the agitation group and the non-agitation group. Factors potentially related to emergence agitation will be collected at study entry, during anaesthesia and operation, during postoperative care. Univariate analyses between the agitation and the non-agitation groups will be performed. The stepwise backward logistic regression will be carried out to identify the independent predictors of agitation. Patients will be followed up for 72 h after the operation. Accidental self-extubation of the endotracheal tube and removal of other catheters will be documented. The use of sedatives and analgesics will be collected. ETHICS AND DISSEMINATION: Ethics approval has been obtained from each of five participating hospitals. Study findings will be disseminated through peer-reviewed publications and conference presentations. TRIAL REGISTRATION NUMBER: NCT02318199.

Membranous expressions of Lewis y and CAM-DR-related markers are independent factors of chemotherapy resistance and poor prognosis in epithelial ovarian cancer.

BACKGROUND: Chemotherapy resistance is a common problem faced by patients diagnosed with epithelial ovarian cancer (EOC). Currently there are no specific or sensitive clinical biomarkers that maybe implemented to identify chemotherapy resistance and give insight to prognosis. The aim of this study is to investigate the roles of Lewis y antigen and the markers associated with cell-adhesion-mediated drug resistance (CAM-DR) in patients with EOC. METHODS: 92 EOC patients who were treated with systemic chemotherapy after cytoreductive surgery were included in this analysis. Patients were divided into two groups, chemotherapy sensitive (n = 56) and resistant (n = 36). Immunohistochemical (IHC) staining for Lewis y and CAM-DR-related cell surface proteins including CD44, CD147, HE4 (Human epididymis protein 4), integrin α5, ß1, αv and ß3 were conducted on tissues collected during primary debulking surgery. Using multivariate logistic regressions, IHC results were compared to clinical variables and chemotherapy resistance to determine possible correlations. The relationships between IHC expression and progression-free survival (PFS) and overall survival (OS) were analyzed using Kaplan-Meier method and Cox regression analysis. RESULTS: Membranous expression of Lewis y and all these CAM-DR-related markers were significantly higher in the resistant group than that of the sensitive group (all P < 0.01). Multivariate regression analysis revealed that high expression of Lewis y, CD44, HE4, integrin α5 and ß1 as well as advanced FIGO stage were independent risk factors for chemotherapy resistance (all P < 0.05). Advanced FIGO stage, lymph node metastasis and high expression of Lewis y, CD44, CD147, HE4, integrin α5, ß1 were associated with a shorter PFS and OS (all P < 0.05). Moreover, multivariate COX analysis demonstrated that the following variates were independent predictors of worse PFS and OS survival: late FIGO stage (P = 0.013, 0.049), high expressions of Lewis y (P = 0.010, 0.036), HE4 (P = 0.006, 0.013) and integrin ß1 (PFS, P = 0.003), integrin α5 (OS, P = 0.019). CONCLUSION: Membranous expression of Lewis y and CAM-DR-related markers including CD44, CD147, HE4, integrin α5, ß1, αv and ß3 are associated with the development of chemotherapy resistance. High expression of Lewis y antigen and CAM-DR-related markers including CD44, CD147, HE4, integrin α5 and ß1 are independent markers for PFS and OS, in which Lewis y and HE4 are the most significant.

Molecular characterization of the hetero-assembly of ß-amyloid peptide with islet amyloid polypeptide.

Increasing amounts of evidence suggest that Alzheimer's disease (AD) and type 2 diabetes (T2D) are linked to each other. We have recently identified in vitro a high affinity interaction between ß-amyloid peptide (Aß) of AD and islet amyloid polypeptide (IAPP) of T2D which results in the formation of non-fibrillar and non-cytotoxic Aß-IAPP hetero-oligomers. The Aß-IAPP interaction delays cytotoxic self-association of both polypeptides albeit it is unable to block it. In this context, IAPP-GI, a soluble conformationally constrained mimic of a non-amyloidogenic and non-toxic IAPP conformer, completely blocks Aß amyloidogenesis and cytotoxicity. Here we studied the hetero-association pathways of Aß with IAPP and with IAPP-GI. We found that preformed Aß or IAPP fibrils and cytotoxic assemblies are able to seed amyloidogenesis and cytotoxicity in Aß-IAPP but not in Aß-IAPP-GI solutions. Initially non-fibrillar and non-toxic Aß-IAPP but not Aß-IAPP-GI hetero-oligomers were found to further aggregate into hetero-fibrils and cytotoxic assemblies in a process strongly enhanced under Aß or IAPP self-assembly promoting conditions. Importantly, our studies provided evidence that initially non-fibrillar and non-toxic Aß-IAPP hetero-oligomers are able to misfold into hetero-fibrils and indicated a crucial role of the strong amyloidogenic character of IAPP in this process. These results uncover a novel molecular property of the Aß and IAPP sequences, i.e. their ability to form hetero-fibrils, and offer mechanistic support to a model linking Aß and IAPP hetero-association to their cytotoxic self-association pathways and thus likely to the pathogenesis of AD and T2D.

Interaction between amyloid beta peptide and an aggregation blocker peptide mimicking islet amyloid polypeptide.

Assembly of amyloid-beta peptide (Aß) into cytotoxic oligomeric and fibrillar aggregates is believed to be a major pathologic event in Alzheimer's disease (AD) and interfering with Aß aggregation is an important strategy in the development of novel therapeutic approaches. Prior studies have shown that the double N-methylated analogue of islet amyloid polypeptide (IAPP) IAPP-GI, which is a conformationally constrained IAPP analogue mimicking a non-amyloidogenic IAPP conformation, is capable of blocking cytotoxic self-assembly of Aß. Here we investigate the interaction of IAPP-GI with Aß40 and Aß42 using NMR spectroscopy. The most pronounced NMR chemical shift changes were observed for residues 13-20, while residues 7-9, 15-16 as well as the C-terminal half of Aß--that is both regions of the Aß sequence that are converted into ß-strands in amyloid fibrils--were less accessible to solvent in the presence of IAPP-GI. At the same time, interaction of IAPP-GI with Aß resulted in a concentration-dependent co-aggregation of Aß and IAPP-GI that was enhanced for the more aggregation prone Aß42 peptide. On the basis of the reduced toxicity of the Aß peptide in the presence of IAPP-GI, our data are consistent with the suggestion that IAPP-GI redirects Aß into nontoxic "off-pathway" aggregates.

Suppression of IAPP fibrillation at anionic lipid membranes via IAPP-derived amyloid inhibitors and insulin.

Aggregation of human islet amyloid polypeptide (hIAPP) into cytotoxic beta-sheet oligomers and amyloid plaques is considered a key event in pancreatic beta-cell degeneration in type 2 diabetes (T2D). hIAPP is synthesized in the pancreatic beta-cells and it is stored, co-processed in the secretory granules, and co-secreted to the extracellular matrix together with insulin. In vivo, hIAPP aggregation may start and proceed at the water-cell membrane interface and anionic lipid membranes strongly enhance the process of hIAPP fibrillization which is causally linked to membrane disintegration and cell degeneration. In this study we explored the amyloidogenic propensity and conformational properties of hIAPP in the presence of negatively charged membrane (DOPC/DOPG phospholipid bilayers) surfaces upon addition of two recently designed potent hIAPP-derived inhibitors of hIAPP amyloidogenesis, the hexapeptide NF(N-Me)GA(N-Me)IL (NFGAIL-GI) and the 37-residue non-amyloidogenic hIAPP analog [(N-Me)G24, (N-Me)I26]-IAPP (IAPP-GI). For comparison, the effects of insulin, which is a natively occurring hIAPP aggregation inhibitor, rat IAPP (rIAPP), which is a natively non-amyloidogenic hIAPP analog, and the hIAPP amyloid core peptide hIAPP(22-27) or NFGAIL were also studied. The aim of our study was to test whether and how the above peptides which have been shown to completely block or suppress hIAPP amyloidogenesis in bulk solution in vitro would also affect these processes in the presence of lipid membranes. To this end, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was applied. We find that IAPP-GI, NFGAIL-GI, insulin, and rIAPP are potent inhibitors of hIAPP fibrillization. Importantly, our data also suggest that the hetero-complexes of IAPP-GI, rIAPP, and insulin with hIAPP although non-amyloidogenic per se are still able to adsorb at the lipid membrane. By contrast, in the presence of NFGAIL-GI, interaction of hIAPP with the lipid membrane is completely abolished, consistent with NFGAIL-GI mediated sequestration of hIAPP via hetero-complexation in the aqueous phase mainly accounting for the observed strong effect of NFGAIL-GI on hIAPP fibrillogenesis at the lipid membrane interface. Finally, our studies show that once hIAPP is fibrillized at the water-lipid membrane interface with fibrils being attached to the lipid membrane, it cannot be disaggregated by all above peptides.

Enhancement of the adhesive and spreading potentials of ovarian carcinoma RMG-1 cells due to increased expression of integrin alpha5beta1 with the Lewis Y-structure on transfection of the alpha1,2-fucosyltransferase gene.

Le(Y) antigen is known to be associated with malignant properties including metastasis and a poor prognosis of ovarian carcinomas. To clarify the mechanisms underling these properties, we established ovarian carcinoma-derived cells exhibiting enhanced expression of Le(Y) by transfection with alpha1,2-fucosyltransferase and compared their cellular properties with those of the original cells. So the human alpha1,2-fucosyltransferase gene was transfected into ovarian carcinoma-derived RMG-1 cells, which are known to contain Le(X), a precursor of Le(Y), and RMG-1-hFUT cells exhibiting enhanced expression of Le(Y) were established by selection with anti-Le(Y) antibodies, and their adhesive and spreading potentials on fibronectin-coated plates were compared with those of RMG-1 cells. Results showed that the relative expression of Le(Y) in RMG-1-hFUT cells was about 20-fold that in RMG-1 cells, and that of integrin alpha5beta1 and an integrin-mediated signal transduction molecule, focal adhesion kinase, was also increased in RMG-1-hFUT cells. Interestingly, anti-Le(Y) antibodies were revealed to immunoprecipitate integrin alpha5beta1, indicating that its oligosaccharides are composed of Le(Y), the amounts of which was substantially elevated in RMG-1-hFUT cells. The adhesion and spreading potentials on fibronectin-coated plates of RMG-1-hFUT cells were significantly enhanced in comparison to those of RMG-1 cells, and were greatly suppressed by anti-Le(Y) antibodies, indicating that Le(Y) is involved in the integrin-fibronectin interaction. These results suggested that transfection of the alpha1,2-fucosyltransferase gene into ovarian carcinoma-derived cells brought about elevated expression of integrin alpha5beta1 with Le(Y), resulting in enhancement of the adhesion and spreading potentials of cells through the integrin-fibronection interaction, which was inhibited by anti-Le(Y) antibodies. Thus, Le(Y) in integrin alpha5beta1 was thought to be involved in the enhanced cell adhesion properties of malignant ovarian carcinomas.

Design of a mimic of nonamyloidogenic and bioactive human islet amyloid polypeptide (IAPP) as nanomolar affinity inhibitor of IAPP cytotoxic fibrillogenesis.

Protein aggregation into cytotoxic oligomers and fibrils in vivo is linked to cell degeneration and the pathogenesis of >25 uncurable diseases, whereas the high aggregation propensity and insolubility of several bioactive polypeptides and proteins in vitro prevent their therapeutic use. Aggregation of human islet amyloid polypeptide (IAPP) into pancreatic amyloid is strongly associated with the pathogenesis of type II diabetes. IAPP is a 37-residue polypeptide that acts as a neuroendocrine regulator of glucose homeostasis. However, IAPP misfolds and self-associates into cytotoxic aggregates and fibrils even at nanomolar concentrations. Because IAPP aggregation causes beta-cell death and prohibits therapeutic application of IAPP in diabetes, we pursued a minimalistic chemical design approach to generate a molecular mimic of a nonamyloidogenic and bioactive IAPP conformation that would still be able to associate with IAPP and thus inhibit its fibrillogenesis and cytotoxicity. We show that the double N-methylated full length IAPP analog [(N-Me)G24, (N-Me)I26]-IAPP (IAPP-GI) is a highly soluble, nonamyloidogenic, and noncytotoxic IAPP molecular mimic and an IAPP receptor agonist. Moreover, IAPP-GI binds IAPP with low nanomolar affinity and completely blocks IAPP cytotoxic self-assembly and fibrillogenesis with activity in the low nanomolar concentration range. Importantly, IAPP-GI dissociates cytotoxic IAPP oligomers and fibrils and is able to reverse their cytotoxicity. Bifunctional soluble IAPP mimics that combine bioactivity with the ability to block and reverse IAPP cytotoxic self-assembly are promising candidates for the treatment of diabetes. Moreover, our amyloid disease inhibitor design concept may be applicable to other protein aggregation diseases.