Vascular endothelial growth factors (VEGFs) regulate blood and lymph vessel development upon activation of three receptor tyrosine kinases: VEGFR-1, -2, and -3. Partial structures of VEGFR/VEGF ...complexes based on single-particle electron microscopy, small-angle X-ray scattering, and X-ray crystallography revealed the location of VEGF binding and domain arrangement of individual receptor subdomains. Here, we describe the structure of the full-length VEGFR-1 extracellular domain in complex with VEGF-A at 4 Å resolution. We combined X-ray crystallography, single-particle electron microscopy, and molecular modeling for structure determination and validation. The structure reveals the molecular details of ligand-induced receptor dimerization, in particular of homotypic receptor interactions in immunoglobulin homology domains 4, 5, and 7. Functional analyses of ligand binding and receptor activation confirm the relevance of these homotypic contacts and identify them as potential therapeutic sites to allosterically inhibit VEGFR-1 activity.
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•First full-length structure of the VEGFR-1 ectodomain bound to its cognate ligand•Description of unique strategy to determine crystal structures at medium resolution•Characterization of VEGFR ligand specificity and homotypic receptor interactions•Paradigm for type V receptor tyrosine kinase activation and therapeutic inhibition
Markovic-Müller et al. describe the first full-length ectodomain structure of a type V receptor tyrosine kinase, VEGFR-1, in complex with its cognate ligand, VEGF-A. The structure reveals the details of regulatory homotypic receptor interactions representing putative targets for therapeutic receptor inhibition.
The receptor-type protein tyrosine phosphatases (RPTPs) are involved in a wide variety of physiological functions which are mediated via their diverse extracellular regions. They play key roles in ...cell-cell contacts, bind various ligands and are regulated by dimerization and other processes. Depending on the subgroup, they have been described as everything from 'rigid rods' to 'floppy tentacles'. Here, we review current experimental structural knowledge on the extracellular region of RPTPs and draw on AlphaFold structural predictions to provide further insights into structure and function of these cellular signalling molecules, which are often mutated in disease and are recognised as drug targets. In agreement with experimental data, AlphaFold predicted structures for extracellular regions of R1, and R2B subgroup RPTPs have an extended conformation, whereas R2B RPTPs are twisted, reflecting their high flexibility. For the R3 PTPs, AlphaFold predicts that members of this subgroup adopt an extended conformation while others are twisted, and that certain members, such as CD148, have one or more large, disordered loop regions in place of fibronectin type 3 domains suggested by sequence analysis.
We presented a 67-year-old nonsmoking female lung adenocarcinoma patient with novel epidermal growth factor receptor (EGFR) A289G/F287_G288insHA cis mutations who responded positively to sintilimab ...combined with regorafenib and albumin paclitaxel, and sequential treatment of icotinib. Gene mutations in patients were detected by next-generation sequencing (NGS) technology, and changes in gene mutations before and after treatments were observed by ctDNA monitoring. We observed the efficacy of the patient through chest computed tomography (CT) imaging and carcinoembryonic antigen (CEA) level and found that the patient benefited from immunotherapy in combination with antiangiogenesis and chemotherapy for more than 1 year, CEA levels initially fell sharply and then rebounded during the treatment period. After changing to EGFR-TKI therapy, the CEA level of the patient does not only decreased sharply at the initial stage of treatment but also rebounded and increased at the later stage of treatment. The patient was tested for genetic mutations after 4 months of sequential EGFR-TKI therapy and was found to have lost all previous EGFR mutations, which may be the cause of resistance to targeted drug icotinib. We believe that our findings have enriched the EGFR mutation spectrum in NSCLC and highlighted the possible choice for patients harboring this mutation by immunotherapy combined with chemotherapy and antivascular therapy, and EGFR-TKI-targeted therapy.
Metabotropic glutamate receptor 7 (mGlu7) regulates neurotransmitter release at the presynaptic active zone in the mammalian brain. The regulation of mGlu7 trafficking into and out of the plasma ...membrane by binding proteins within the C‐terminal region of mGlu7 governs the bidirectional synaptic plasticity. However, the functional importance of the extracellular domain of mGlu7 has not yet been characterized. N‐glycosylation is an abundant posttranslational modification that plays crucial roles in protein folding and forward trafficking, but the role of N‐glycosylation in mGlu7 function remains unknown. In this study, we find that mGlu7 is N‐glycosylated at four asparagine residues in heterologous cells and rat cultured neurons. We demonstrate that N‐glycosylation is essential for forward transport and surface expression of mGlu7. Deglycosylated mGlu7 is retained in the ER, obstructing expression on the cell surface, and is degraded through the autophagolysosomal degradation pathway. In addition, we identify the binding domain of mGlu7 to Elfn1, a transsynaptic adhesion protein. We find that N‐glycosylation of mGlu7 promotes its interaction with Elfn1, thereby enabling proper localization and stable surface expression of mGlu7 at the presynaptic active zone. These findings provide evidence that N‐glycans act to modulate the surface expression, stability, and function of mGlu7.
Nicotinic acetylcholine receptors (nAChRs) are integral membrane proteins and prototypic members of the ligand-gated ion-channel superfamily, which has precursors in the prokaryotic world. They are ...formed by the assembly of five transmembrane subunits, selected from a pool of 17 homologous polypeptides (alpha1-10, beta1-4, gamma, delta, and epsilon). There are many nAChR subtypes, each consisting of a specific combination of subunits, which mediate diverse physiological functions. They are widely expressed in the central nervous system, while, in the periphery, they mediate synaptic transmission at the neuromuscular junction and ganglia. nAChRs are also found in non-neuronal/nonmuscle cells (keratinocytes, epithelia, macrophages, etc.). Extensive research has determined the specific function of several nAChR subtypes. nAChRs are now important therapeutic targets for various diseases, including myasthenia gravis, Alzheimer's and Parkinson's diseases, and schizophrenia, as well as for the cessation of smoking. However, knowledge is still incomplete, largely because of a lack of high-resolution X-ray structures for these molecules. Nevertheless, electron microscopy studies on 2D crystals of nAChR from fish electric organs and the determination of the high-resolution X-ray structure of the acetylcholine binding protein (AChBP) from snails, a homolog of the extracellular domain of the nAChR, have been major steps forward and the data obtained have important implications for the design of subtype-specific drugs. Here, we review some of the latest advances in our understanding of nAChRs and their involvement in physiology and pathology.
Background
Tetraspanin‐7 (Tspan7) is an islet autoantigen involved in autoimmune type 1 diabetes and known to regulate β‐cell L‐type Ca2+ channel activity. However, the role of Tspan7 in pancreatic ...β‐cell function is not yet fully understood.
Methods
Histological analyses were conducted using immunostaining. Whole‐body metabolism was tested using glucose tolerance test. Islet hormone secretion was quantified using static batch incubation or dynamic perifusion. β‐cell transmembrane currents, electrical activity and exocytosis were measured using whole‐cell patch‐clamping and capacitance measurements. Gene expression was studied using mRNA‐sequencing and quantitative PCR.
Results
Tspan7 is expressed in insulin‐containing granules of pancreatic β‐cells and glucagon‐producing α‐cells. Tspan7 knockout mice (Tspan7y/− mouse) exhibit reduced body weight and ad libitum plasma glucose but normal glucose tolerance. Tspan7y/− islets have normal insulin content and glucose‐ or tolbutamide‐stimulated insulin secretion. Depolarisation‐triggered Ca2+ current was enhanced in Tspan7y/− β‐cells, but β‐cell electrical activity and depolarisation‐evoked exocytosis were unchanged suggesting that exocytosis was less sensitive to Ca2+. TSPAN7 knockdown (KD) in human pseudo‐islets led to a significant reduction in insulin secretion stimulated by 20 mM K+. Transcriptomic analyses show that TSPAN7 KD in human pseudo‐islets correlated with changes in genes involved in hormone secretion, apoptosis and ER stress. Consistent with rodent β‐cells, exocytotic Ca2+ sensitivity was reduced in a human β‐cell line (EndoC‐βH1) following Tspan7 KD.
Conclusion
Tspan7 is involved in the regulation of Ca2+‐dependent exocytosis in β‐cells. Its function is more significant in human β‐cells than their rodent counterparts.
Precision medicine with gene panel testing based on next-generation sequencing for patients with cancer is being used increasingly in clinical practice. HER2, which encodes the human epidermal growth ...factor receptor 2 (HER2), is a potentially important driver gene. However, therapeutic strategies aimed at mutations in the HER2 extracellular domain have not been clarified. We therefore investigated the effect of EGFR co-targeted therapy with HER2 on patient-derived cancer models with the HER2 extracellular domain mutation E401G, based on our previous findings that this mutation has an epidermal growth factor receptor (EGFR)-mediated activation mechanism.
We generated a xenograft (PDX) and a cancer tissue-originated spheroid (CTOS) from a patient's cancer containing an amplified HER2 E401G mutation. With these platforms, we compared the efficacy of afatinib, a tyrosine kinase inhibitor having anti-HER2 and anti-EGFR activity, with two other therapeutic options: lapatinib, which has similar properties but weaker EGFR inhibition, and trastuzumab plus pertuzumab, for which evidence exists of treatment efficacy against cancers with wild-type HER2 amplification. Similar experiments were also performed with H2170, a cell line with wild-type HER2 amplification, to contrast the characteristics of these drug's efficacies against HER2 E401G.
We confirmed that PDX and CTOS retained morphological and immunohistochemical characteristics and HER2 gene profiles of the original tumor. In both PDX and CTOS, afatinib reduced tumor size more than lapatinib or trastuzumab plus pertuzumab. In addition, afatinib treatment resulted in a statistically significant reduction in HER2 copy number at the end of treatment. On the other hand, in H2170 xenografts with wild-type HER2 amplification, trastuzumab plus pertuzumab was most effective.
Afatinib, a dual inhibitor of HER2 and EGFR, showed a promising effect on cancers with amplified HER2 E401G, which have an EGFR-mediated activation mechanism. Analysis of the activation mechanisms of mutations and development of therapeutic strategies based on those mechanisms are critical in precision medicine for cancer patients.
Background
Patients with poorly cohesive gastric carcinoma (PCC) are known to have poor survival. However, detailed molecular biology of PCC has not been elucidated, except for mutations in
CDH1
and
...RHOA
. Additionally, the molecular profiles of signet-ring cell carcinoma (SRC) have not been fully investigated. We aimed to investigate the association between molecular profiles and survival in PCC and PCC subtypes.
Methods
The present study included 455 patients with gastric adenocarcinoma underwent radical gastrectomy. Whole-exome sequencing and gene expression profiling were conducted. Patients were classified according to the WHO classification as PCC or non-PCC, with PCC being further classified into SRC, combined, and PCC not-otherwise-specified (NOS). Clinicopathological factors and survival were compared with molecular profiles.
Results
Of the patients, 159 were classified with PCC, while 296 were classified with non-PCC. Among PCC, 44 were classified with SRC, 64 with combined, and 51 with PCC-NOS. Mutations in
CDH1
and
RHOA
were remarkably more frequent in PCC than in non-PCC. PCC had worse overall survival (OS) and disease-specific survival (DSS) compared to non-PCC. For PCC, the SRC group had good OS and DSS, whereas PCC-NOS classification with
CDH1
mutations was associated with extremely poor survival. In the PCC-NOS and combined groups, patients with mutations in the extracellular domain 1 of
CDH1
had poor survival.
Conclusions
Our findings suggest that PCC has poorer survival than non-PCC. Accumulation of
CDH1
and
RHOA
mutations are unique profiles in PCC. Among PCC,
CDH1
mutations may play a crucial role in the survival of non-SRC PCC.
The transmembrane metalloprotease ADAM10 sheds a range of cell surface proteins, including ligands and receptors of the Notch, Eph, and erbB families, thereby activating signaling pathways critical ...for tumor initiation and maintenance. ADAM10 is thus a promising therapeutic target. Although widely expressed, its activity is normally tightly regulated. We now report prevalence of an active form of ADAM10 in tumors compared with normal tissues, in mouse models and humans, identified by our conformation-specific antibody mAb 8C7. Structure/function experiments indicate mAb 8C7 binds an active conformation dependent on disulfide isomerization and oxidative conditions, common in tumors. Moreover, this active ADAM10 form marks cancer stem-like cells with active Notch signaling, known to mediate chemoresistance. Importantly, specific targeting of active ADAM10 with 8C7 inhibits Notch activity and tumor growth in mouse models, particularly regrowth after chemotherapy. Our results indicate targeted inhibition of active ADAM10 as a potential therapy for ADAM10-dependent tumor development and drug resistance.
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