ArticlePDF Available

Assessing the range of kinase autoinhibition mechanisms in the insulin receptor family

Authors:
Stephen Artim at Massachusetts Institute of Technology
Stephen Artim
Jeannine M Mendrola
Jeannine M Mendrola
Jeannine M Mendrola
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Mark Lemmon at Yale University
Mark Lemmon
Download full-text PDFDownload full-text PDF
Read full-text
Download citation

Abstract and Figures

To investigate the range of autoinhibitory mechanisms used by tyrosine kinase domains (TKDs) from the insulin receptor family of receptor tyrosine kinases, we determined crystal structures of TKDs from TrkA (nerve growth factor receptor) and Ror2 (an unconventional Wnt receptor). TrkA autoinhibition closely resembles that seen for insulin receptor, relying on projection of an activation loop tyrosine into the substrate binding site and occlusion of the ATP binding site by the activation loop. Ror2 employs similar mechanisms, but the unusual replacement of the phenylalanine in its Asp-Phe-Gly motif with leucine necessitates occlusion of the ATP-binding site by other means. The unusual Asp-Leu-Gly motif in Ror2 is displaced compared with other inactive kinases, allowing the activation loop to interact directly with the TKDs alphaC helix, in another mode of autoinhibition that is characteristic of the other extreme of this receptor family ALK and Met. These findings provide insight into the expected range of activating mutations in these TKDs in cancer. We also describe a symmetric dimer of the inactive TrkA TKD resembling that found in other receptor tyrosine kinases - possibly reflecting an arrangement of kinase domains in a pre-formed TrkA dimer.
Structures of TrkA and Ror2 TKDs Structures of inactive TKDs from TrkA (left) and Ror2 (right) in cartoon representation. The N-lobe and C-lobe are labelled, as is the catalytically important αC helix. The activation loops are labelled and highlighted in cyan (TrkA) and magenta (Ror2). Side chains in the DFG motif of TrkA (Asp 668-Phe 669-Gly 670 ) and the equivalently located DLG motif in Ror2 (Asp 633-Leu 634-Gly 635 ) are shown, and tyrosine residues from the YXXXYY motif are shown in stick representation. Also shown is the invariant lysine residue in strand β3 (Lys 544 in TrkA, Lys 507 in Ror2), which forms a salt bridge with αC Glu 524 in Ror2 (but not TrkA). The catalytic base aspartate (Asp 650 in TrkA, Asp 615 in Ror2) is also shown and labelled. Molecule A was used for Ror2 TKD. The N-and C-terminal residues of the modelled structure are marked where visible in the orientation shown.
Structures of TrkA and Ror2 TKDs Structures of inactive TKDs from TrkA (left) and Ror2 (right) in cartoon representation. The N-lobe and C-lobe are labelled, as is the catalytically important αC helix. The activation loops are labelled and highlighted in cyan (TrkA) and magenta (Ror2). Side chains in the DFG motif of TrkA (Asp 668-Phe 669-Gly 670 ) and the equivalently located DLG motif in Ror2 (Asp 633-Leu 634-Gly 635 ) are shown, and tyrosine residues from the YXXXYY motif are shown in stick representation. Also shown is the invariant lysine residue in strand β3 (Lys 544 in TrkA, Lys 507 in Ror2), which forms a salt bridge with αC Glu 524 in Ror2 (but not TrkA). The catalytic base aspartate (Asp 650 in TrkA, Asp 615 in Ror2) is also shown and labelled. Molecule A was used for Ror2 TKD. The N-and C-terminal residues of the modelled structure are marked where visible in the orientation shown.
… 
ATP-binding-site occlusion by the activation loop in inactive IRK, TrkA and Ror2
ATP-binding-site occlusion by the activation loop in inactive IRK, TrkA and Ror2
… 
Structures of inactive TKDs from TrkA (left) and Ror2 (right) in cartoon representation. The N-lobe and C-lobe are labelled, as is the catalytically important αC helix. The activation loops are labelled and highlighted in cyan (TrkA) and magenta (Ror2). Side chains in the DFG motif of TrkA (Asp668-Phe669-Gly670) and the equivalently located DLG motif in Ror2 (Asp633-Leu634-Gly635) are shown, and tyrosine residues from the YXXXYY motif are shown in stick representation. Also shown is the invariant lysine residue in strand β3 (Lys544 in TrkA, Lys507 in Ror2), which forms a salt bridge with αC Glu524 in Ror2 (but not TrkA). The catalytic base aspartate (Asp650 in TrkA, Asp615 in Ror2) is also shown and labelled. Molecule A was used for Ror2 TKD. The N- and C-terminal residues of the modelled structure are marked where visible in the orientation shown.
Structures of inactive TKDs from TrkA (left) and Ror2 (right) in cartoon representation. The N-lobe and C-lobe are labelled, as is the catalytically important αC helix. The activation loops are labelled and highlighted in cyan (TrkA) and magenta (Ror2). Side chains in the DFG motif of TrkA (Asp668-Phe669-Gly670) and the equivalently located DLG motif in Ror2 (Asp633-Leu634-Gly635) are shown, and tyrosine residues from the YXXXYY motif are shown in stick representation. Also shown is the invariant lysine residue in strand β3 (Lys544 in TrkA, Lys507 in Ror2), which forms a salt bridge with αC Glu524 in Ror2 (but not TrkA). The catalytic base aspartate (Asp650 in TrkA, Asp615 in Ror2) is also shown and labelled. Molecule A was used for Ror2 TKD. The N- and C-terminal residues of the modelled structure are marked where visible in the orientation shown.
… 
Known inactive conformation structures of IRK family kinases (in addition to TrkA and Ror2) were overlaid on that of the insulin receptor (PDB code 1IRK [13]; grey, with the TKD shown in surface representation), and their activation loops coloured. (A) The activation loops of MuSK (PDB code 1LUF [15]; orange), TrkA (cyan), Ror2 molecule A (magenta) and IGF1R (PDB code 1M7N [14]; yellow) align well with that of IRK. (B) The activation loops of Ron (PDB code 3PLS [17]; red), Met (PDB code 2G15 [16]; blue) and ALK (PDB code 3L9P [8]; green) are more widely variable and are compared with that of IRK (grey). Tyrosine side chains in the YXXXYY motif are shown, and the substrate-mimicking tyrosine residue (Tyr1162 in IRK) is marked with a red asterisk.
Known inactive conformation structures of IRK family kinases (in addition to TrkA and Ror2) were overlaid on that of the insulin receptor (PDB code 1IRK [13]; grey, with the TKD shown in surface representation), and their activation loops coloured. (A) The activation loops of MuSK (PDB code 1LUF [15]; orange), TrkA (cyan), Ror2 molecule A (magenta) and IGF1R (PDB code 1M7N [14]; yellow) align well with that of IRK. (B) The activation loops of Ron (PDB code 3PLS [17]; red), Met (PDB code 2G15 [16]; blue) and ALK (PDB code 3L9P [8]; green) are more widely variable and are compared with that of IRK (grey). Tyrosine side chains in the YXXXYY motif are shown, and the substrate-mimicking tyrosine residue (Tyr1162 in IRK) is marked with a red asterisk.
… 
Structures of the inactive TKDs from IRK [13], TrkA and Ror2 were overlaid on the structure of active IRK (PDB code 1IR3) determined with bound peptide substrate and a non-hydrolysable ATP analogue AMP-PNP (adenosine 5′-[β,γ-imido]triphosphate) [41]. Close-up views of residues surrounding the binding site for AMP-PNP (shown from the 1IR3 structure) are shown for inactive IRK (activation loop coloured grey), TrkA (activation loop coloured cyan) and Ror2 (activation loop coloured magenta). Whereas the 1IR3 (active) structure readily accommodates AMP-PNP, the nucleotide-binding site is occluded directly by the activation loop in inactive IRK, TrkA and Ror2, with backbone and side-chain clashes with the phosphate groups. In addition, the DFG motif phenylalanine residue (Phe1151 in IRK and Phe669 in TrkA) blocks the binding site for the adenine ring of AMP-PNP. This inhibitory interaction is not maintained in Ror2, which has a phenylalanine-to-leucine substitution in the DFG motif (yielding DLG), and Tyr555 from elsewhere in the TKD takes an a similar role.
+3
Structures of the inactive TKDs from IRK [13], TrkA and Ror2 were overlaid on the structure of active IRK (PDB code 1IR3) determined with bound peptide substrate and a non-hydrolysable ATP analogue AMP-PNP (adenosine 5′-[β,γ-imido]triphosphate) [41]. Close-up views of residues surrounding the binding site for AMP-PNP (shown from the 1IR3 structure) are shown for inactive IRK (activation loop coloured grey), TrkA (activation loop coloured cyan) and Ror2 (activation loop coloured magenta). Whereas the 1IR3 (active) structure readily accommodates AMP-PNP, the nucleotide-binding site is occluded directly by the activation loop in inactive IRK, TrkA and Ror2, with backbone and side-chain clashes with the phosphate groups. In addition, the DFG motif phenylalanine residue (Phe1151 in IRK and Phe669 in TrkA) blocks the binding site for the adenine ring of AMP-PNP. This inhibitory interaction is not maintained in Ror2, which has a phenylalanine-to-leucine substitution in the DFG motif (yielding DLG), and Tyr555 from elsewhere in the TKD takes an a similar role.
… 
Figures - uploaded by Mark Lemmon
Author content
All figure content in this area was uploaded by Mark Lemmon
Content may be subject to copyright.
54360cdd0cf2643ab986a3
ad.pdf
Content uploaded by Mark Lemmon
Author content
All content in this area was uploaded by Mark Lemmon on Oct 09, 2014
Content may be subject to copyright.
Assessing the range of kinase autoinhibition mechanisms in the insulin receptor fami
ly.pdf
Available via license: CC BY-NC 2.5
Content may be subject to copyright.
A preview of the PDF is not available
... Another important divergence is the shift from DFG to DLG that has occurred between mammals and some apicomplexans. DLG is associated with inactive or less-active kinases such as receptor tyrosine kinase like orphan receptor 2 (ROR2) (30,31), and the selective pressure that led to this mutation is not yet clear, because DFG-mutated tachyzoites behave normally in cell cultures (Fig. 2, D to F). DLF conversion to DFG results in resistance to altiratinib, both in vivo and in vitro activity assays. This observation, although counterintuitive, is not unique, as other resistance-conferring mutations in Abl, RET, and EGFR have been shown to promote resistance by increasing kinase activity without altering the binding properties of the drug (32)(33)(34). ...
Altiratinib blocks Toxoplasma gondii and Plasmodium falciparum development by selectively targeting a spliceosome kinase
Article
  • Aug 2022
The Apicomplexa comprise a large phylum of single-celled, obligate intracellular protozoa that include Toxoplasma gondii , Plasmodium , and Cryptosporidium spp., which infect humans and animals and cause severe parasitic diseases. Available therapeutics against these diseases are limited by suboptimal efficacy and frequent side effects, as well as the emergence and spread of resistance. We use a drug repurposing strategy and identify altiratinib, a compound originally developed to treat glioblastoma, as a promising drug candidate with broad spectrum activity against apicomplexans. Altiratinib is parasiticidal and blocks the development of intracellular zoites in the nanomolar range and with a high selectivity index when used against T. gondii . We have identified Tg PRP4K of T. gondii as the primary target of altiratinib using genetic target deconvolution, which highlighted key residues within the kinase catalytic site that conferred drug resistance when mutated. We have further elucidated the molecular basis of the inhibitory mechanism and species selectivity of altiratinib for Tg PRP4K and for its Plasmodium falciparum counterpart, Pf CLK3. Our data identified structural features critical for binding of the other Pf CLK3 inhibitor, TCMDC-135051. Consistent with the splicing control activity of this kinase family, we have shown that altiratinib can cause global disruption of splicing, primarily through intron retention in both T. gondii and P. falciparum . Thus, our data establish parasitic PRP4K/CLK3 as a potential pan-apicomplexan target whose repertoire of inhibitors can be expanded by the addition of altiratinib.
View
... The IR-A recognizes insulin and IGF and has a higher affinity for IGF2 than IGF1. As IR-B is specific for insulin, it is involved in glucose homeostasis [74]. ...
Impact of metabolic syndrome on the risk of endometrial cancer and the role of lifestyle in prevention
Article
Full-text available
  • Feb 2022
Endometrial cancer is the second gynecological cancer with the highest global incidence. Among many associated risk factors, Among the risk factors, metabolic syndrome is an important and preventable one. It comprises a group of conditions that often occur together: central adiposity, hyperglycemia, arterial hypertension, and atherogenic dyslipidemia. This review aimed to describe the epidemiological and biological relationship between metabolic syndrome and endometrial cancer, focusing on the role of lifestyle in prevention. A literature search was carried out in the PubMed database. 4824 publications were screened, and 123 were included for this review. The association between metabolic syndrome and endometrial cancer has been described. Chronic adipose tissue inflammation and insulin resistance are involved in the development of obesity, particularly visceral adiposity. These changes promote the ideal environment for the development of endometrial cancer. Strategies based on lifestyle modifications may be effective for the prevention of metabolic syndrome and consequently endometrial cancer. Some of these modifications include adopting a diet rich in fruits, vegetables, whole grains, and legumes, depending to the accessibility of these foods for each region. Avoiding ultra-processed foods and increasing daily physical activity were also some suggested modifications. We propose that women be screened for metabolic syndrome to establish early treatment and to possibly prevent endometrial cancer. Clinical trials designed to prove the effect of lifestyle modifications on the prevention of endometrial cancer are needed.
View
... Insulin is not only a metabolic hormone but also a cell growth factor that can stimulate the mitogenic cascade by activating the MAPK and mTOR pathways. Its functions are mediated by binding to two receptors: IR-A, which recognizes insulin and more specifically insulin-like growth factors (IGFs) 1 and 2; and IR-B, which is an insulin-specific receptor [93]. ...
Obesity and Thyroid Cancer Risk: An Update
Article
Full-text available
Thyroid cancer (TC) is the most common endocrine malignancy worldwide and its incidence has increased dramatically in recent years. In parallel, the prevalence of overweight and obesity has also increased, suggesting a possible link between these two diseases. Indeed, low-grade chronic inflammation, altered cytokine levels, insulin resistance, oxidative stress, and hormonal changes that occur in obese patients are all factors that contribute to the occurrence and growth of TC. In this review, the most recent evidence supporting the potential role of the mechanisms linking obesity to TC will be discussed.
View
Structure and function of the ROR2 cysteine-rich domain in vertebrate noncanonical WNT5A signaling
Article
Full-text available
  • May 2024
  • eLife
The receptor tyrosine kinase ROR2 mediates noncanonical WNT5A signaling to orchestrate tissue morphogenetic processes, and dysfunction of the pathway causes Robinow syndrome, Brachydactyly B and metastatic diseases. The domain(s) and mechanisms required for ROR2 function, however, remain unclear. We solved the crystal structure of the extracellular cysteine-rich (CRD) and Kringle (Kr) domains of ROR2 and found that, unlike other CRDs, the ROR2 CRD lacks the signature hydrophobic pocket that binds lipids/lipid-modified proteins, such as WNTs, suggesting a novel mechanism of ligand reception. Functionally, we showed that the ROR2 CRD, but not other domains, is required and minimally sufficient to promote WNT5A signaling, and Robinow mutations in the CRD and the adjacent Kr impair ROR2 secretion and function. Moreover, using function-activating and -perturbing antibodies against the Frizzled (FZ) family of WNT receptors, we demonstrate the involvement of FZ in WNT5A-ROR signaling. Thus, ROR2 acts via its CRD to potentiate the function of a receptor super-complex that includes FZ to transduce WNT5A signals.
View
View
ROR2 homodimerization is sufficient to activate a neuronal Wnt/calcium signaling pathway
Article
Full-text available
  • Oct 2023
  • J BIOL CHEM
Wnt signaling plays a key role in the mature CNS by regulating trafficking of NMDA-type glutamate receptors and intrinsic properties of neurons. The Wnt receptor ROR2 has been identified as a necessary component of the neuronal Wnt5a/Ca²⁺ signaling pathway that regulates synaptic and neuronal function. Since ROR2 is considered a pseudokinase, its mechanism for downstream signaling upon ligand binding has been controversial. It has been suggested that its role is to function as a coreceptor of a G-protein–coupled Wnt receptor of the Frizzled family. We show that chemically induced homodimerization of ROR2 is sufficient to recapitulate key signaling events downstream of receptor activation in neurons, including PKC and JNK kinases activation, elevation of somatic and dendritic Ca²⁺ levels, and increased trafficking of NMDARs to synapses. In addition, we show that homodimerization of ROR2 induces phosphorylation of the receptor on Tyr residues. Point mutations in the conserved but presumed nonfunctional ATP-binding site of the receptor prevent its phosphorylation, as well as downstream signaling. This suggests an active kinase domain. Our results indicate that ROR2 can signal independently of Frizzled receptors to regulate the trafficking of a key synaptic component. Additionally, they suggest that homodimerization can overcome structural conformations that render the tyrosine kinase inactive. A better understanding of ROR2 signaling is crucial for comprehending the regulation of synaptic and neuronal function in normal brain processes in mature animals.
View
Receptor Tyrosine Kinases and Their Ligands
Chapter
  • Aug 2022
The 58 human receptor tyrosine kinases (RTKs) have important functions in the regulation of cell proliferation, survival, and migration during embryonal development and in adult tissue. RTKs divide into 20 subfamilies based on their extracellular regions. In most cases binding of the activating ligand leads to RTK dimerization and/or formation of higher-order oligomers, which promotes activation of the kinase by autophosphorylation in trans. Additional phosphorylation of regulatory tyrosines leads to recruitment of downstream signaling molecules via interaction of SH2 (Src homology 2) domains and other phosphotyrosine binding domains. Aberrant activation of RTKs is implicated in numerous disease states including cancer.
View
Looking lively: emerging principles of pseudokinase signaling
Article
  • May 2022
  • TRENDS BIOCHEM SCI
Progress towards understanding catalytically 'dead' protein kinases – pseudokinases – in biology and disease has hastened over the past decade. An especially lively area for structural biology, pseudokinases appear to be strikingly similar to their kinase relatives, despite lacking key catalytic residues. Distinct active- and inactive-like conformation states, which are crucial for regulating bona fide protein kinases, are conserved in pseudokinases and appear to be essential for function. We discuss recent structural data on conformational transitions and nucleotide binding by pseudokinases, from which some common principles emerge. In both pseudokinases and bona fide kinases, a conformational toggle appears to control the ability to interact with signaling effectors. We also discuss how biasing this conformational toggle may provide opportunities to target pseudokinases pharmacologically in disease.
View
Dynamics of protein kinases and pseudokinases by HDX-MS
Chapter
  • Apr 2022
  • METHOD ENZYMOL
Dynamics of the protein kinase fold are deeply intertwined with its structure. The past three decades of kinase biophysical studies revealed key dynamic features of the kinase domain and, more recently, how these features may endow catalytically impaired kinases—or pseudokinases—with signaling properties. Hydrogen-deuterium exchange coupled with mass spectrometry (HDX-MS) is proving to be a valuable approach for studies of kinase and pseudokinase domain dynamics. Here, we briefly discuss the methods that have provided insights into protein kinase dynamics, describe how HDX-MS is being used to answer questions in the kinase/pseudokinase field, and provide a detailed protocol for collecting an HDX-MS dataset to study the impacts of small molecule binding to a pseudokinase domain. As more small molecules are discovered that can disrupt pseudokinase conformations, HDX-MS is likely to be a powerful approach for exploring drug-induced changes in pseudokinase dynamics and structure.
View
Cellular and Molecular Mechanisms Implicated in the Dual Role of ROR2 in Cancer
Article
Full-text available
  • Jan 2022
  • CRIT REV ONCOL HEMAT
ROR1 and ROR2 are Wnt receptors that are critical for β-catenin-independent Wnt pathways and were have been linked to processes driving tumor progression, such as cell proliferation, survival, invasion, and therapy resistance. Both receptors have garnered interest as potential therapeutic targets since they are largely absent in adult tissue, are overexpressed in several cancers, and, as members of the receptor tyrosine kinase family, are easier to target than all other components of the pathway. Unlike ROR1 which always promotes tumorigenesis, ROR2 has a very complex role in cancer acting either to promote or inhibit tumor progression in different tumor types. In the present article, we summarize the findings on ROR2 expression in cancer patients and its impact on clinical outcome. Further, we review the biological processes and signaling pathways regulated by ROR2 that explain its dual role in cancer. Finally, we describe the ongoing strategies to target ROR2 in cancer.
View
Discovery of GNF-5837, a Selective TRK Inhibitor with Efficacy in Rodent Cancer Tumor Models
Article
Full-text available
  • Feb 2012
Neurotrophins and their receptors (TRKs) play key roles in the development of the nervous system and the maintenance of the neural network. Accumulating evidence points to their role in malignant transformations, chemotaxis, metastasis, and survival signaling and may contribute to the pathogenesis of a variety of tumors of both neural and non-neural origin. By screening the GNF kinase collection, a series of novel oxindole inhibitors of TRKs were identified. Optimization led to the identification of GNF-5837 (22), a potent, selective, and orally bioavailable pan-TRK inhibitor that inhibited tumor growth in a mouse xenograft model derived from RIE cells expressing both TRKA and NGF. The properties of 22 make it a good tool for the elucidation of TRK biology in cancer and other nononcology indications.
View
Processing of X-ray diffraction data
Article
Full-text available
  • Dec 1997
Publisher Summary X-ray data can be collected with zero-, one-, and two-dimensional detectors, zero-dimensional (single counter) being the simplest and two-dimensional the most efficient in terms of measuring diffracted X-rays in all directions. To analyze the single-crystal diffraction data collected with these detectors, several computer programs have been developed. Two-dimensional detectors and related software are now predominantly used to measure and integrate diffraction from single crystals of biological macromolecules. Macromolecular crystallography is an iterative process. To monitor the progress, the HKL package provides two tools: (1) statistics, both weighted (χ 2 ) and unweighted (R-merge), where the Bayesian reasoning and multicomponent error model helps obtain proper error estimates and (2) visualization of the process, which helps an operator to confirm that the process of data reduction, including the resulting statistics, is correct and allows the evaluation of the problems for which there are no good statistical criteria. Visualization also provides confidence that the point of diminishing returns in data collection and reduction has been reached. At that point, the effort should be directed to solving the structure. The methods presented in the chapter have been applied to solve a large variety of problems, from inorganic molecules with 5 A unit cell to rotavirus of 700 A diameters crystallized in 700 × 1000 × 1400 A cell.
View
ROR1 and ROR2 in Human Malignancies: Potentials for Targeted Therapy
Article
Full-text available
  • Apr 2012
Targeted therapies require cellular protein expression that meets specific requirements that will maximize effectiveness, minimize off-target toxicities, and provide an opportunity for a therapeutic effect. The receptor tyrosine kinase-like orphan receptors (ROR) are possible targets for therapy that may meet such requirements. RORs are transmembrane proteins that are part of the receptor tyrosine kinase (RTK) family. The RORs have been shown to play a role in tumor-like behavior, such as cell migration and cell invasiveness and are normally not expressed in normal adult tissue. As part of the large effort in target discovery, ROR proteins have recently been found to be expressed in human cancers. Their unique expression profiles may provide a novel class of therapeutic targets for small molecules against the kinase or for antibody-based therapies against these receptors. Being restricted on tumor cells and not on most normal tissues, RORs are excellent targets for the treatment of minimal residual disease, the final hurdle in the curative approach to many cancers, including solid tumors such as neuroblastoma. In this review, we summarize the biology of RORs as they relate to human cancer, and highlight the therapeutic approaches directed toward them.
View
View
View
The CCP4 Suite: Programs for Protein Crystallography
Article
  • Sep 1994
The CCP4 (Collaborative Computational Project, number 4) program suite is a collection of programs and associated data and subroutine libraries which can be used for macromolecular structure determination by X-ray crystallography. The suite is designed to be flexible, allowing users a number of methods of achieving their aims and so there may be more than one program to cover each function. The programs are written mainly in standard Fortran77. They are from a wide variety of sources but are connected by standard data file formats. The package has been ported to all the major platforms under both Unix and VMS. The suite is distributed by anonymous ftp from Daresbury Laboratory and is widely used throughout the world.
View
Discovery of Disubstituted Imidazo[4,5- b ]pyridines and Purines as Potent TrkA Inhibitors
Article
  • Sep 2012
Trk receptor tyrosine kinases have been implicated in cancer and pain. A crystal structure of TrkA with AZ-23 (1a) was obtained, and scaffold hopping resulted in two 5/6-bicyclic series comprising either imidazo[4,5-b]pyridines or purines. Further optimization of these two fusion series led to compounds with subnanomolar potencies against TrkA kinase in cellular assays. Antitumor effects in a TrkA-driven mouse allograft model were demonstrated with compounds 2d and 3a.
View
Crystal Structure of the MuSK Tyrosine Kinase
Article
  • Sep 2002
Muscle-specific kinase (MuSK) is a receptor tyrosine kinase expressed selectively in skeletal muscle. During neuromuscular synapse formation, agrin released from motor neurons stimulates MuSK autophosphorylation in the kinase activation loop and in the juxtamembrane region, leading to clustering of acetylcholine receptors. We have determined the crystal structure of the cytoplasmic domain of unphosphorylated MuSK at 2.05 Å resolution. The structure reveals an autoinhibited kinase domain in which the activation loop obstructs ATP and substrate binding. Steady-state kinetic analysis demonstrates that autophosphorylation results in a 200-fold increase in kcat and a 10-fold decrease in the Km for ATP. These studies provide a molecular basis for understanding the regulation of MuSK catalytic activity and suggest that an additional in vivo component may contribute to regulation via the juxtamembrane region.
View
View
Targeting ALK in neuroblastoma-preclinical and clinical advancements
Article
  • May 2012
  • NAT REV CLIN ONCOL
Despite improvements in cancer therapies in the past 50 years, neuroblastoma remains a devastating clinical problem and a leading cause of childhood cancer deaths. Advances in treatments for children with high-risk neuroblastoma have, until recently, involved addition of cytotoxic therapy to dose-intensive regimens. In this era of targeted therapies, substantial efforts have been made to identify optimal targets for different types of cancer. The discovery of hereditary and somatic activating mutations in the oncogene ALK has now placed neuroblastoma among other cancers, such as melanoma and non-small-cell lung cancer (NSCLC), which benefit from therapies with oncogene-specific small-molecule tyrosine kinase inhibitors. Crizotinib, a small-molecule inhibitor of ALK, has transformed the landscape for the treatment of NSCLC harbouring ALK translocations and has demonstrated activity in preclinical models of ALK-driven neuroblastomas. However, inhibition of mutated ALK is complex when compared with translocated ALK and remains a therapeutic challenge. This Review discusses the biology of ALK in the development of neuroblastoma, preclinical and clinical progress with the use of ALK inhibitors and immunotherapy, challenges associated with resistance to such therapies and the steps being taken to overcome some of these hurdles.
View