Use of protease substrate specificity screening in the rational design of selective protease inhibitors with unnatural amino acids: Application to HGFA, matriptase, and hepsin.

Inhibition of the proteolytic processing of hepatocyte growth factor (HGF) and macrophage stimulating protein (MSP) is an attractive approach for the drug discovery of novel anticancer therapeutics which prevent tumor progression and metastasis. Here, we utilized an improved and expanded version of positional scanning of substrate combinatorial libraries (PS-SCL) technique called HyCoSuL to optimize peptidomimetic inhibitors of the HGF/MSP activating serine proteases, HGFA, matriptase, and hepsin. These inhibitors have an electrophilic ketone serine trapping warhead and thus form a reversible covalent bond to the protease. We demonstrate that by varying the P2, P3, and P4 positions of the inhibitor with unnatural amino acids based on the protease substrate preferences learned from HyCoSuL, we can predictably modify the potency and selectivity of the inhibitor. We identified the tetrapeptide JH-1144 (8) as a single digit nM inhibitor of HGFA, matriptase and hepsin with excellent selectivity over Factor Xa and thrombin. These unnatural peptides have increased metabolic stability relative to natural peptides of similar structure. The tripeptide inhibitor PK-1-89 (2) has excellent pharmacokinetics in mice with good compound exposure out to 24 h. In addition, we obtained an X-ray structure of the inhibitor MM1132 (15) bound to matriptase revealing an interesting binding conformation useful for future inhibitor design.

Circulating TNF-RII, IP-10 and HGF are associated with severity of COVID-19 in oncologic patients.

The COVID-19 patients showed hyperinflammatory response depending on the severity of the disease but little have been reported about this response in oncologic patients that also were infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Sixty-five circulating cytokines/chemokines were quantified in 15 oncologic patients, just after SARS-CoV-2 infection and fourteen days later, and their levels were compared in patients who required hospitalisation by COVID-19 versus non-hospitalised patients. A higher median age of 72 years (range 61-83) in oncologic patients after SARS-CoV-2 infection was associated with hospitalisation requirement by COVID-19 versus a median age of 49 years (20-75) observed in the non-hospitalised oncologic patients (p = 0.008). Moreover, oncologic patients at metastatic stage or with lung cancer were significantly associated with hospitalisation by COVID-19 (p = 0.044). None of these hospitalised patients required ICU treatment. Higher basal levels of tumour necrosis factor receptor II (TNF-RII), interferon-γ (IFNγ)-induced protein 10 (IP-10) and hepatocyte growth factor (HGF) in plasma were significantly observed in oncologic patients who required hospitalisation by COVID-19. Higher TNF-RII, IP-10 and HGF levels after the SARS-CoV-2 infection in oncologic patients could be used as biomarkers of COVID-19 severity associated with hospitalisation requirements.

Dimer Interface in Natural Variant NK1 Is Dispensable for HGF-Dependent Met Receptor Activation.

NK1, a splicing variant of hepatocyte growth factor (HGF), binds to and activates Met receptor by forming an NK1 dimer and 2:2 complex with Met. Although the structural mechanism underlying Met activation by HGF remains incompletely resolved, it has been proposed that the NK1 dimer structure participates in this activation. We investigated the NK1 dimer interface's role in Met activation by HGF. Because N127, V140, and K144 are closely involved in the head-to-tail NK1 dimer formation, mutant NK1 proteins with replacement of these residues by alanine were prepared. In Met tyrosine phosphorylation assays, N127-NK1, V140-NK1, and K144-NK1 showed 8.3%, 23.8%, and 52.2% activity, respectively, compared with wild-type NK1. Although wild-type NK1 promoted cell migration and scattering, N127-NK1, V140-NK1, and K144-NK1 hardly or marginally promoted them, indicating loss of activity of these mutant NK1 proteins to activate Met. In contrast, mutant HGFs (N127-HGF, V140-HGF, and K144-HGF) with the same amino acid replacements as in NK1 induced Met tyrosine phosphorylation and biological responses at levels comparable to those of wild-type HGF. These results indicate that the structural basis responsible for NK1-dependent Met dimer formation and activation differs from, or is at least distinguishable from, the structural basis responsible for HGF-dependent Met activation.

Photoreactive Molecular Glue for Enhancing the Efficacy of DNA Aptamers by Temporary-to-Permanent Conjugation with Target Proteins.

We developed a photoreactive molecular glue, BPGlue-N3, which can provide a universal strategy to enhance the efficacy of DNA aptamers by temporary-to-permanent stepwise stabilization of their conjugates with target proteins. As a proof-of-concept study, we applied BPGlue-N3 to the SL1 (DNA aptamer)/c-Met (target protein) conjugate system. BPGlue-N3 can adhere to and temporarily stabilize this aptamer/protein conjugate multivalently using its guanidinium ion (Gu+) pendants that form a salt bridge with oxyanionic moieties (e.g., carboxylate and phosphate) and benzophenone (BP) group that is highly affinitive to DNA duplexes. BPGlue-N3 is designed to carry a dual-mode photoreactivity; upon exposure to UV light, the temporarily stabilized aptamer/protein conjugate reacts with the photoexcited BP unit of adhering BPGlue-N3 and also a nitrene species, possibly generated by the BP-to-N3 energy transfer in BPGlue-N3. We confirmed that SL1, covalently conjugated with c-Met, hampered the binding of hepatocyte growth factor (HGF) onto c-Met, even when the SL1/c-Met conjugate was rinsed prior to the treatment with HGF, and suppressed cell migration caused by HGF-induced c-Met phosphorylation.

Urinary Kringle Domain-Containing Protein HGFL: A Validated Biomarker of Early Sickle Cell Anemia-Associated Kidney Disease.

INTRODUCTION: Chronic kidney disease (CKD) is a prevalent complication of sickle cell anemia (SCA). Hyperfiltration that delayed detection of CKD is common in SCA patients. Identification of novel urinary biomarkers correlating with glomerular filtration rates may help to detect and predict progression of renal disease. METHODS: Reanalysis of mass spectra of urinary samples obtained from University of Illinois at Chicago identified kringle domain-containing protein HGFL. RESULTS: HGFL levels correlated with hyperfiltration, were significantly reduced at CKD stage 1 compared to stage 0, negatively correlated with progression of CKD and were suitable for differentiation of stage 1. Better prediction of CKD progression to stage 2 was observed for HGFL-based risk prediction compared to the estimated glomerular filtration rate (eGFR)-based prediction. Results from a Howard University patient cohort supported the utility of HGFL-based test for the differentiation of stage 1 of CKD. CONCLUSION: Urinary HGFL may contribute additional information beyond eGFR and improve diagnosis of early-stage CKD in SCA patients.

Structural basis of the activation of c-MET receptor.

The c-MET receptor is a receptor tyrosine kinase (RTK) that plays essential roles in normal cell development and motility. Aberrant activation of c-MET can lead to both tumors growth and metastatic progression of cancer cells. C-MET can be activated by either hepatocyte growth factor (HGF), or its natural isoform NK1. Here, we report the cryo-EM structures of c-MET/HGF and c-MET/NK1 complexes in the active state. The c-MET/HGF complex structure reveals that, by utilizing two distinct interfaces, one HGF molecule is sufficient to induce a specific dimerization mode of c-MET for receptor activation. The binding of heparin as well as a second HGF to the 2:1 c-MET:HGF complex further stabilize this active conformation. Distinct to HGF, NK1 forms a stable dimer, and bridges two c-METs in a symmetrical manner for activation. Collectively, our studies provide structural insights into the activation mechanisms of c-MET, and reveal how two isoforms of the same ligand use dramatically different mechanisms to activate the receptor.

Supramolecular Self-Assembled Nanofibers Efficiently Activate the Precursor of Hepatocyte Growth Factor for Angiogenesis in Myocardial Infarction Therapy.

The reconstruction of blood perfusion is a crucial therapeutic method to save and protect cardiac function after acute myocardial infarction (AMI). The activation of the hepatocyte growth factor precursor (pro-HGF) has a significant effect on promoting angiogenesis and antiapoptosis. The oxygen/glucose deprivation (OGD) caused by AMI could induce vascular adventitia fibroblasts to differentiate into myofibroblasts and secrete the pro-HGF. Meanwhile, the specific Met receptor of the hepatocyte growth factor (HGF) is upregulated in endothelial cells during AMI. However, the poor prognosis of AMI suggests that the pro-HGF is not effectively activated. Improving the activation efficiency of the pro-HGF may play a positive role in the treatment of AMI. Herein, we designed supramolecular nanofibers self-assembled by compound 1 (Comp.1, Nap-FFEG-IVGGYPWWMDV), which can strongly activate the pro-HGF and initiate HGF-Met signaling. Studies have proven that Comp.1 possesses a better ability to activate the pro-HGF to perform antiapoptosis and pro-angiogenesis. In vivo results have confirmed that the retention time of Comp.1 and its accumulation in the infarct area of the heart are promoted. Moreover, Comp.1 plays an effective role in promoting angiogenesis in the marginal area of AMI, reducing myocardial fibrosis, and protecting cardiac function. Herein, we will optimize the structure of bioactive peptides through supramolecular self-assembly and amplify their therapeutic effect by improving their efficiency, providing a new strategy for the therapy of AMI.

State of the structure address on MET receptor activation by HGF.

The MET receptor tyrosine kinase (RTK) and its cognate ligand hepatocyte growth factor (HGF) comprise a signaling axis essential for development, wound healing and tissue homeostasis. Aberrant HGF/MET signaling is a driver of many cancers and contributes to drug resistance to several approved therapeutics targeting other RTKs, making MET itself an important drug target. In RTKs, homeostatic receptor signaling is dependent on autoinhibition in the absence of ligand binding and orchestrated set of conformational changes induced by ligand-mediated receptor dimerization that result in activation of the intracellular kinase domains. A fundamental understanding of these mechanisms in the MET receptor remains incomplete, despite decades of research. This is due in part to the complex structure of the HGF ligand, which remains unknown in its full-length form, and a lack of high-resolution structures of the complete MET extracellular portion in an apo or ligand-bound state. A current view of HGF-dependent MET activation has evolved from biochemical and structural studies of HGF and MET fragments and here we review what these findings have thus far revealed.

Scan and Unlock: A Programmable DNA Molecular Automaton for Cell-Selective Activation of Ligand-Based Signaling.

Selective modulation of ligand-receptor interaction is essential in targeted therapy. In this study, we design an intelligent "scan and unlock" DNA automaton (SUDA) system to equip a native protein-ligand with cell-identity recognition and receptor-mediated signaling in a cell-type-specific manner. Using embedded DNA-based chemical reaction networks (CRNs) on the cell surface, SUDA scans and evaluates molecular profiles of cell-surface proteins via Boolean logic circuits. Therefore, it achieves cell-specific signal modulation by quickly unlocking the protein-ligand in proximity to the target cell-surface to activate its cognate receptor. As a proof of concept, we non-genetically engineered hepatic growth factor (HGF) with distinct logic SUDAs to elicit target cell-specific HGF signaling and wound healing behaviors in multiple heterogeneous cell types. Furthermore, the versatility of the SUDA strategy was shown by engineering tumor necrotic factor-α (TNFα) to induce programmed cell death of target cell subpopulations through cell-specific modulation of TNFR1 signaling.

Immunogenicity Risk Assessment for PEGylated Therapeutics.

The objective of this manuscript is to provide the reader with two examples on how to present an immunogenicity risk assessment for a PEGylated therapeutic as part of Investigational New Drug (IND) application or during other stages of the drug development process. In order to provide context to the bioanalytical strategies used to support the PEGylated therapeutics presented here, a brief summary of information available for marketed PEGylated biologics is provided. Two case studies are presented, a PEGylated enzyme and a PEGylated growth factor. For the former, the risk assessment covers how to deal with a narrow therapeutic window and suggestions to utilize a PD marker as surrogate for neutralizing antibody assessments in Phase I. The latter has recommendations on additional analytes that should be monitored to mitigate risk of immunogenicity to endogenous counterparts.

Molecular Glue that Spatiotemporally Turns on Protein-Protein Interactions.

We developed a dendritic molecular glue PCGlue-NBD that can serve universally to "turn on" protein-protein interactions (PPIs) spatiotemporally. PCGlue-NBD carrying multiple guanidinium ion (Gu+) pendants can adhere strongly to target proteins and cover their surfaces including the PPI interface regions, thereby suppressing PPIs with their receptor proteins. Upon irradiation with UV light, PCGlue-NBD on a target protein is photocleaved at butyrate-substituted nitroveratryloxycarbonyl linkages in the dendrimer framework, so that the multivalency for the adhesion is reduced. Consequently, the guest protein is liberated and becomes eligible for a PPI. We found that hepatocyte growth factor HGF, when mixed with PCGlue-NBD, lost the affinity toward its receptor c-Met. However, upon exposure of the PCGlue-NBD/HGF hybrid to light-emitting diode light (365 nm), the PCGlue-NBD molecules on HGF were photocleaved as described above, so that HGF was liberated and retrieved its intrinsic PPI affinity toward c-Met. The turn-on PPI, thus achieved for HGF and c-Met, leads to cell migration, which can be made spatiotemporally with a millimeter-scale resolution by pointwise irradiation with UV light.

The MEK-ERK-MST1 Axis Potentiates the Activation of the Extrinsic Apoptotic Pathway during GDC-0941 Treatment in Jurkat T Cells.

The discrete activation of individual caspases is essential during T-cell development, activation, and apoptosis. Humans carrying nonfunctional caspase-8 and caspase-8 conditional knockout mice exhibit several defects in the progression of naive CD4⁺ T cells to the effector stage. MST1, a key kinase of the Hippo signaling pathway, is often presented as a substrate of caspases, and its cleavage by caspases potentiates its activity. Several studies have focused on the involvement of MST1 in caspase activation and also reported several defects in the immune system function caused by MST1 deficiency. Here, we show the rapid activation of the MEK-ERK-MST1 axis together with the cleavage and activation of caspase-3, -6, -7, -8, and -9 after PI3K signaling blockade by the selective inhibitor GDC-0941 in Jurkat T cells. We determined the phosphorylation pattern of MST1 using a phosphoproteomic approach and identified two amino acid residues phosphorylated in an ERK-dependent manner after GDC-0941 treatment together with a novel phosphorylation site at S21 residue, which was extensively phosphorylated in an ERK-independent manner during PI3K signaling blockade. Using caspase inhibitors and the inhibition of MST1 expression using siRNA, we identified an exclusive role of the MEK-ERK-MST1 axis in the activation of initiator caspase-8, which in turn activates executive caspase-3/-7 that finally potentiate MST1 proteolytic cleavage. This mechanism forms a positive feed-back loop that amplifies the activation of MST1 together with apoptotic response in Jurkat T cells during PI3K inhibition. Altogether, we propose a novel MEK-ERK-MST1-CASP8-CASP3/7 apoptotic pathway in Jurkat T cells and believe that the regulation of this pathway can open novel possibilities in systemic and cancer therapies.

Overexpressing kringle 1 domain of hepatocyte growth factor with adeno-associated virus inhibits the pathological retinal neovascularization in an oxygen-induced retinopathy mouse model.

Current clinical treatments for ocular neovascularization are characterized by high possibility of damaging healthy tissues and high recurrence rates. It is necessary to develop new treatment methods to control neovascularization with a stable and effective effect. Kringle1 domain of hepatocyte growth factor (HGFK1) has anti-angiogenesis activity. Here, we established oxygen-induced retinopathy (OIR) model to study if using adeno-associated virus (AAV) as a delivery system to overexpression HGFK1 in retinal cells could benefit retinal neovascularization. We show that, overexpressed exogenous gene was mainly expressed in the inner and outer nuclear layer of the retina. Compared with control mice, the mice pretreated with rAAV-HGFK1 at P3 showed relatively normal vascular branches examined by fluorescence fundus angiography. Subsequent H&E staining and immunohistochemical staining of CD31 of the eye tissue sections showed that the mice received rAAV-HGFK1 had a relatively normal distribution of vascular endothelial cells. Additionally, immunohistochemical staining indicated a lower expression of VEGF in the eye tissues of rAAV-HGFK1 treated OIR mice. Further in vitro studies showed that HGFK1 could inhibit the proliferation but promote the apoptosis of bovine retinal microvascular endothelial cells (BRECs) under the presence of VEGF. Moreover, HGFK1 could inhibit VEGF induced ERK activation but promote p38 activation in BRECs. Therefore, we propose that intravitreal injection of rAAV-HGFK1 might be used to improve the retinal neovascularization and HGFK1 may function through regulating VEGF signaling pathway to inhibit neovascularization.

Isolation and Characterization of a Chinese Hamster Ovary Heparan Sulfate Cell Mutant Defective in Both Met Receptor Binding and Hepatocyte Growth Factor NK1/Met Signaling.

BACKGROUND/AIMS: The up-regulation of hepatocyte growth factor/receptor, HGF/Met, signal transduction is observed in most of human cancers. Specific heparan sulfate structures enhance the HGF/Met signaling at both cell and animal-based model systems. Biochemical studies indicate that heparan sulfate interacts with HGF and a natural occurring splicing variant NK1 of HGF with similar affinity. However, it is currently unknown if cell surface heparan sulfate binds to Met at physiological conditions and if specific cell surface heparan sulfate structures are required for effective HGF/Met or NK1/Met signaling. METHODS: An established flow sorting strategy was used to isolate a soluble Met recombinant protein-binding positive or negative CHO cell clones different only in specific heparan sulfate structures. The cell surface bindings were imaged by confocal microscopy and flow cytometry analysis. Glucosamine vs. galactosamine contents from media-, cell surface-, and cell association glycosaminoglycans were quantified by HPLC. 35S-sulfate labeled glycosaminoglycans were characterized by anion exchange and size-exclusion HPLC. Heparan sulfate disaccharide compositions were determined by HPLC-MS analysis. Western blot analyses of MAPK-p42/44 were used to monitor HGF- and NK1-facillated Met signaling. RESULTS: CHO-Positive but not CHO-Negative cell surface heparan sulfate bound to Met recombinant protein and HGF/NK1 further promoted the binding. Overall glycosaminoglycan analysis results indicated that the CHO-Negative cells had reduced amount of heparan sulfate, shorter chain length, and less 6-O-sulfated disaccharides compared to that of CHO-Positive cells. Moreover, CHO-Negative cells were defective in NK1/Met but not HGF/Met signaling. CONCLUSIONS: This study demonstrated that soluble Met recombinant protein bound to cell surface HS at physiological conditions and a Met /HGF or NK1/HS ternary signaling complex might be involved in Met signaling. Shorter HS chains and reduced 6-O-sulfation might be responsible for reduced Met binding and the diminished NK1-initiated signaling in the CHO-Negative cells. The unique CHO-Positive and CHO-Negative cell clones established in current study should be effective tools for studying the role of specific glycosaminoglycan structures in regulating Met signaling. Such knowledge should be useful in developing glycosaminoglycan-based compounds that target HGF/Met signaling.

The MST4-MOB4 complex disrupts the MST1-MOB1 complex in the Hippo-YAP pathway and plays a pro-oncogenic role in pancreatic cancer.

The mammalian STE20-like protein kinase 1 (MST1)-MOB kinase activator 1 (MOB1) complex has been shown to suppress the oncogenic activity of Yes-associated protein (YAP) in the mammalian Hippo pathway, which is involved in the development of multiple tumors, including pancreatic cancer (PC). However, it remains unclear whether other MST-MOB complexes are also involved in regulating Hippo-YAP signaling and have potential roles in PC. Here, we report that mammalian STE20-like kinase 4 (MST4), a distantly related ortholog of the MST1 kinase, forms a complex with MOB4 in a phosphorylation-dependent manner. We found that the overall structure of the MST4-MOB4 complex resembles that of the MST1-MOB1 complex, even though the two complexes exhibited opposite biological functions in PC. In contrast to the tumor-suppressor effect of the MST1-MOB1 complex, the MST4-MOB4 complex promoted growth and migration of PANC-1 cells. Moreover, expression levels of MST4 and MOB4 were elevated in PC and were positively correlated with each other, whereas MST1 expression was down-regulated. Because of divergent evolution of key interface residues, MST4 and MOB4 could disrupt assembly of the MST1-MOB1 complex through alternative pairing and thereby increased YAP activity. Collectively, these findings identify the MST4-MOB4 complex as a noncanonical regulator of the Hippo-YAP pathway with an oncogenic role in PC. Our findings highlight that although MST-MOB complexes display some structural conservation, they functionally diverged during their evolution.

Structural Basis for Auto-Inhibition of the NDR1 Kinase Domain by an Atypically Long Activation Segment.

The human NDR family kinases control diverse aspects of cell growth, and are regulated through phosphorylation and association with scaffolds such as MOB1. Here, we report the crystal structure of the human NDR1 kinase domain in its non-phosphorylated state, revealing a fully resolved atypically long activation segment that blocks substrate binding and stabilizes a non-productive position of helix αC. Consistent with an auto-inhibitory function, mutations within the activation segment of NDR1 dramatically enhance in vitro kinase activity. Interestingly, NDR1 catalytic activity is further potentiated by MOB1 binding, suggesting that regulation through modulation of the activation segment and by MOB1 binding are mechanistically distinct. Lastly, deleting the auto-inhibitory activation segment of NDR1 causes a marked increase in the association with upstream Hippo pathway components and the Furry scaffold. These findings provide a point of departure for future efforts to explore the cellular functions and the mechanism of NDR1.

H1/pHGFK1 nanoparticles exert anti-tumoural and radiosensitising effects by inhibition of MET in glioblastoma.

BACKGROUND: The therapeutic resistance to ionising radiation (IR) and anti-angiogenesis mainly impair the prognosis of patients with glioblastoma. The primary and secondary MET aberrant activation is one crucial factor for these resistances. The kringle 1 domain of hepatocyte growth factor (HGFK1), an angiogenic inhibitor, contains a high-affinity binding domain of MET; however, its effects on glioblastoma remain elusive. METHODS: We formed the nanoparticles consisting of a folate receptor-targeted nanoparticle-mediated HGFK1 gene (H1/pHGFK1) and studied its anti-tumoural and radiosensitive activities in both subcutaneous and orthotopic human glioma cell-xenografted mouse models. We then elucidated its molecular mechanisms in human glioblastoma cell lines in vitro. RESULTS: We demonstrated for the first time that peritumoural injection of H1/pHGFK1 nanoparticles significantly inhibited tumour growth and prolonged survival in tumour-bearing mice, as well as enhanced the anti-tumoural efficacies of IR in vivo by reducing Ki-67 expression, enhancing TUNEL staining-indicated apoptotic indexes, reducing microvascular intensity and reversing IR-induced MET overexpression in tumour tissues. Furthermore, we showed that HGFK1 suppressed the proliferation and induced cell apoptosis and enhanced sensitivity to IR in glioblastoma cell lines, mainly by suppressing the activities of MET receptor, down-regulating ATM-Chk2 axis but up-regulating Chk1. CONCLUSIONS: H1/pHGFK1 exerts anti-tumoural and radiosensitive activities mainly through the inhibition and reversal of IR-induced MET and ATM-Chk2 axis activities in glioblastoma. H1/pHGFK1 nanoparticles are a potential radiosensitiser and angiogenic inhibitor for glioblastoma treatment.

Isolation and molecular cloning of hepatocyte growth factor from guinea pig (gHGF), and expression of truncated variant of gHGF with improved anti-fibrotic activity in Escherichia coli.

Hepatocyte growth factor (HGF) is an attractive target for anti-fibrotic therapy because it attenuates excessive transforming growth factor-ß1 (TGF-ß1) which plays an important role in hepatic fibrosis. In the study, we reported on the isolation and molecular cloning of the open reading frame (ORF) of guinea pig HGF (gHGF), encoding a protein of 729 amino acids, with an apple-like (hairpin) domain, four kringle domains and a trypsin-like serine protease domain. Moreover, the truncated variant of gHGF (a double mutant of N-terminal hairpin and first kringle domains of gHGF, K132E and G134E, gmNK1) protein fused with His6 tag, the molecular weight of which was about 20.0kDa, which was expressed in Escherichia coli BL21 (DE3) and purified with Ni2+-affinity chromatography. Furthermore, gmNK1 inhibited protein expression levels of fibrosis-related type I collagen (Col I) and α-smooth muscle actin (α-SMA) genes in TGF-ß1-activated HSC-T6 cells and CCl4-induced liver fibrosis in rat. In addition, gmNK1 ameliorated liver morphology and fibrotic responses in fibrosis animal. Taken together, we first reported on the sequence of HGF from guinea pig and determined the anti-fibrotic activity of gmNK1 in hepatic fibrosis, which will be helpful for investigations into the biological roles of gHGF in this important animal model.

[Association between hepatocyte growth factor in tears and corneal haze in rabbits early after epipolis laser in situ keratomileusis].

OBJECTIVE: To study the dynamic changes of levels of hepatocyte growth factor (HGF) in tears and their association with corneal haze in rabbits early after epipolis laser in situ keratomileusis (Epi-LASIK). METHODS: Twenty-four New Zealand rabbits received Epi-LASIK with an ablation depth of 100 µm in one eye and of 150 µm in the other eye. Before and at 3, 7, 14, and 30 days after the surgery, the level of HGF in tears collected from the rabbits was measured using enzyme-linked immunosorbent assay (ELISA), and corneal haze was graded after surgery. RESULTS: In all the rabbits, corneal epithelium healing occurred in 3 to 5 days after Epi-LASIK. Corneal haze appeared 3 days postoperatively in the rabbits accompanied by increased levels of HGF in tears. At 3, 7, 14, and 30 days after the surgery, the rabbits with an ablation depth of 150 µm showed more obvious corneal haze (P<0.05) and significantly higher levels of HGF in tears than those with an ablation depth of 100 µm (P<0.05). CONCLUSION: In rabbits receiving Epi-LASIK, HGF levels in tears and the grade of corneal haze show a positive correlation early after the surgery and are both related with the depth of ablation.

Research progresses on the molecular structure of the Hippo signaling pathway components.

The Hippo signaling pathway has been identified to be involved in development and tissue homeostasis during the past decade, and is evolutionarily conserved from Drosophila to mammals. It transduces the signal through a series of protein-protein interaction and kinase cascades, to control the cell number and organ size by inhibiting cell proliferation and promoting apoptosis. Dysregulation of the Hippo signaling pathway is associated with tumorigenesis and cancers, so it is a crucial target for cancer therapy and regeneration medicine. Most of the Hippo signaling pathway components have been identified, and the cellular function and molecular mechanism have been revealed by structural and functional researches. In this review, we summarize the molecular structure of Hippo signaling pathway components and related targeting inhibitors from a structural view. We hope to improve the understandings of the regulation mechanism of the Hippo signaling transduction, and facilitate further functional studies and potential therapeutic interventions.