scholarly journals Specific Eph Receptor-Cytoplasmic Effector Signaling Mediated by SAM-SAM Domain Interactions

2018 ◽  
Author(s):  
Yue Wang ◽  
Yuan Shang ◽  
Jianchao Li ◽  
Weidi Chen ◽  
Gang Li ◽  
...  
Keyword(s):  
Cell Biology ◽  
Eph Receptors ◽  
Eph Receptor ◽  
X Ray ◽  
Binding Partner ◽  
Sam Domain ◽  
Domain Interactions ◽  
Circuit Formation ◽  
Exquisite Specificity ◽  
Effector Binding

AbstractThe Eph receptor tyrosine kinase (RTK) family is the largest subfamily of RTKs playing critical roles in many developmental processes such as tissue patterning, neurogenesis and neuronal circuit formation, angiogenesis, etc. How the 14 Eph proteins, via their highly similar cytoplasmic domains, can transmit diverse and sometimes opposite cellular signals upon engaging ephrins is a major unresolved question. Here we systematically investigated the bindings of each SAM domain of Eph receptors to the SAM domains from SHIP2 and Odin, and uncover a highly specific SAM-SAM interaction-mediated cytoplasmic Eph-effector binding pattern. Comparative X-ray crystallographic studies of several SAM-SAM heterodimer complexes, together with biochemical and cell biology experiments, not only revealed the exquisite specificity code governing Eph/effector interactions but also allowed us to identify SAMD5 as a new Eph binding partner. Finally, these Eph/effector SAM heterodimer structures can explain numerous Eph SAM mutations identified in patients suffering from cancers and other diseases.

scholarly journals Specific Eph receptor-cytoplasmic effector signaling mediated by SAM–SAM domain interactions

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Yue Wang ◽  
Yuan Shang ◽  
Jianchao Li ◽  
Weidi Chen ◽  
Gang Li ◽  
...  
Keyword(s):  
Cell Biology ◽  
Eph Receptors ◽  
Eph Receptor ◽  
X Ray ◽  
Binding Partner ◽  
Sam Domain ◽  
Domain Interactions ◽  
Circuit Formation ◽  
Exquisite Specificity ◽  
Effector Binding

The Eph receptor tyrosine kinase (RTK) family is the largest subfamily of RTKs playing critical roles in many developmental processes such as tissue patterning, neurogenesis and neuronal circuit formation, angiogenesis, etc. How the 14 Eph proteins, via their highly similar cytoplasmic domains, can transmit diverse and sometimes opposite cellular signals upon engaging ephrins is a major unresolved question. Here, we systematically investigated the bindings of each SAM domain of Eph receptors to the SAM domains from SHIP2 and Odin, and uncover a highly specific SAM–SAM interaction-mediated cytoplasmic Eph-effector binding pattern. Comparative X-ray crystallographic studies of several SAM–SAM heterodimer complexes, together with biochemical and cell biology experiments, not only revealed the exquisite specificity code governing Eph/effector interactions but also allowed us to identify SAMD5 as a new Eph binding partner. Finally, these Eph/effector SAM heterodimer structures can explain many Eph SAM mutations identified in patients suffering from cancers and other diseases.

scholarly journals Author response: Specific Eph receptor-cytoplasmic effector signaling mediated by SAM–SAM domain interactions

2018 ◽  
Author(s):  
Yue Wang ◽  
Yuan Shang ◽  
Jianchao Li ◽  
Weidi Chen ◽  
Gang Li ◽  
...  
Keyword(s):  
Author Response ◽  
Eph Receptor ◽  
Sam Domain ◽  
Domain Interactions

scholarly journals The EphB6 Receptor: Kinase-Dead but Very Much Alive

2021 ◽  
Vol 22 (15) ◽  
pp. 8211
Author(s):  
Timothy G. Strozen ◽  
Jessica C. Sharpe ◽  
Evelyn D. Harris ◽  
Maruti Uppalapati ◽  
Behzad M. Toosi
Keyword(s):  
Signal Transduction ◽  
Molecular Mechanisms ◽  
Biological Effects ◽  
Adaptor Proteins ◽  
Molecular Switch ◽  
Comparative Approach ◽  
Eph Receptors ◽  
Eph Receptor ◽  
Sam Domain ◽  
Receptor Clusters

The Eph receptor tyrosine kinase member EphB6 is a pseudokinase, and similar to other pseudoenzymes has not attracted an equivalent amount of interest as its enzymatically-active counterparts. However, a greater appreciation for the role pseudoenzymes perform in expanding the repertoire of signals generated by signal transduction systems has fostered more interest in the field. EphB6 acts as a molecular switch that is capable of modulating the signal transduction output of Eph receptor clusters. Although the biological effects of EphB6 activity are well defined, the molecular mechanisms of EphB6 function remain enigmatic. In this review, we use a comparative approach to postulate how EphB6 acts as a scaffold to recruit adaptor proteins to an Eph receptor cluster and how this function is regulated. We suggest that the evolutionary repurposing of EphB6 into a kinase-independent molecular switch in mammals has involved repurposing the kinase activation loop into an SH3 domain-binding site. In addition, we suggest that EphB6 employs the same SAM domain linker and juxtamembrane domain allosteric regulatory mechanisms that are used in kinase-positive Eph receptors to regulate its scaffold function. As a result, although kinase-dead, EphB6 remains a strategically active component of Eph receptor signaling.

Defects of Platelet Function Recognized by X-Ray Imaging and Scanning Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 610-613
Author(s):  
M.G. Baldini ◽  
S. Morinaga ◽  
D. Minasian ◽  
R. Feder ◽  
D. Sayre ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Biology ◽  
Imaging Technique ◽  
Human Platelets ◽  
X Rays ◽  
X Ray ◽  
X Ray Imaging ◽  
Complex Phenomena ◽  
Scanning Electron

Contact X-ray imaging is presently developing as an important imaging technique in cell biology. Our recent studies on human platelets have demonstrated that the cytoskeleton of these cells contains photondense structures which can preferentially be imaged by soft X-ray imaging. Our present research has dealt with platelet activation, i.e., the complex phenomena which precede platelet appregation and are associated with profound changes in platelet cytoskeleton. Human platelets suspended in plasma were used. Whole cell mounts were fixed and dehydrated, then exposed to a stationary source of soft X-rays as previously described. Developed replicas and respective grids were studied by scanning electron microscopy (SEM).

scholarly journals The Shb scaffold binds the Nck adaptor protein, p120 RasGAP, and Chimaerins and thereby facilitates heterotypic cell segregation by the receptor EphB2

2020 ◽  
Vol 295 (12) ◽  
pp. 3932-3944 ◽  
Author(s):  
Melany J. Wagner ◽  
Marilyn S. Hsiung ◽  
Gerald D. Gish ◽  
Rick D. Bagshaw ◽  
Sasha A. Doodnauth ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Cell Movement ◽  
Adaptor Protein ◽  
Receptor Activation ◽  
Sh2 Domain ◽  
Tumor Formation ◽  
Eph Receptors ◽  
Eph Receptor ◽  
Varied Composition ◽  
Cell Segregation

Eph receptors are a family of receptor tyrosine kinases that control directional cell movement during various biological processes, including embryogenesis, neuronal pathfinding, and tumor formation. The biochemical pathways of Eph receptors are context-dependent in part because of the varied composition of a heterotypic, oligomeric, active Eph receptor complex. Downstream of the Eph receptors, little is known about the essential phosphorylation events that define the context and instruct cell movement. Here, we define a pathway that is required for Eph receptor B2 (EphB2)–mediated cell sorting and is conserved among multiple Eph receptors. Utilizing a HEK293 model of EphB2+/ephrinB1+ cell segregation, we found that the scaffold adaptor protein SH2 domain–containing adaptor protein B (Shb) is essential for EphB2 functionality. Further characterization revealed that Shb interacts with known modulators of cytoskeletal rearrangement and cell mobility, including Nck adaptor protein (Nck), p120-Ras GTPase-activating protein (RasGAP), and the α- and β-Chimaerin Rac GAPs. We noted that phosphorylation of Tyr297, Tyr246, and Tyr336 of Shb is required for EphB2–ephrinB1 boundary formation, as well as binding of Nck, RasGAP, and the chimaerins, respectively. Similar complexes were formed in the context of EphA4, EphA8, EphB2, and EphB4 receptor activation. These results indicate that phosphotyrosine-mediated signaling through Shb is essential in EphB2-mediated heterotypic cell segregation and suggest a conserved function for Shb downstream of multiple Eph receptors.

scholarly journals Cellular Uptake, DNA Binding and Apoptosis Induction of Cytotoxic Trans-[PtCl2(N,N-dimethylamine)(Isopropylamine)] in A2780cisR Ovarian Tumor Cells

2001 ◽  
Vol 8 (1) ◽  
pp. 29-37 ◽  
Author(s):  
José M. Pérez ◽  
Eva I. Montero ◽  
Adoración G. Quiroga ◽  
Miguel A Fuertes ◽  
Carlos Alonso ◽  
...  
Keyword(s):  
Dna Binding ◽  
Cytotoxic Activity ◽  
Cellular Uptake ◽  
Cell Biology ◽  
Resistant Cell ◽  
Resistant Cell Line ◽  
Platinum Compound ◽  
X Ray ◽  
Molecular Cell Biology ◽  
Ovarian Tumor Cells

Trans-[PtCl2(N,N-dimethylamine)(isopropylamine)] is a novel trans-platinum compound that shows cytotoxic activity in several cisplatin resistant cell lines. The aim of this paper was to analyse, by means of molecular cell biology techniques and total reflection X-ray fluorescence (TXRF), the cytotoxic activity, the induction of apoptosis, the cellular uptake and the DNA binding of trans-[PtCl2(N,N-dimethylamine)(isopropylamine)] in the cisplatin resistant cell line A2780cisR. The results show that this drug is more cytotoxic and induces a higher amount of apoptotic cells than cisplatin in A2780cisR cells. However, the intracellular accumulation and extent of binding to DNA of trans-[PtCl2(N,N-dimethylamine)( isopropylamine)] is lower than that of cis-DDP. Moreover, trans-[PtCl2(N,N-dimethylamine)(isopropylaminae)] is partially inactivated by intracellular levels of glulathione. The result suggest that circumvention of ciplatin resistance by trans-[PtCl2(N,N-dimethylamine)(isopropylamine)] in A2780cisR cells might be related with the ability of this drug to induce apoptosis.

scholarly journals Eph receptor function is modulated by heterooligomerization of A and B type Eph receptors

2011 ◽  
Vol 195 (6) ◽  
pp. 1033-1045 ◽  
Author(s):  
Peter W. Janes ◽  
Bettina Griesshaber ◽  
Lakmali Atapattu ◽  
Eva Nievergall ◽  
Linda L. Hii ◽  
...  
Keyword(s):  
Cellular Responses ◽  
Eph Receptors ◽  
Wild Type ◽  
Eph Receptor ◽  
Receptor Complexes ◽  
Ephb Receptor ◽  
Receptor Profile ◽  
Ephrin Ligands ◽  
The Individual ◽  
Cross Inhibition

Eph receptors interact with ephrin ligands on adjacent cells to facilitate tissue patterning during normal and oncogenic development, in which unscheduled expression and somatic mutations contribute to tumor progression. EphA and B subtypes preferentially bind A- and B-type ephrins, respectively, resulting in receptor complexes that propagate via homotypic Eph–Eph interactions. We now show that EphA and B receptors cocluster, such that specific ligation of one receptor promotes recruitment and cross-activation of the other. Remarkably, coexpression of a kinase-inactive mutant EphA3 with wild-type EphB2 can cause either cross-activation or cross-inhibition, depending on relative expression. Our findings indicate that cellular responses to ephrin contact are determined by the EphA/EphB receptor profile on a given cell rather than the individual Eph subclass. Importantly, they imply that in tumor cells coexpressing different Ephs, functional mutations in one subtype may cause phenotypes that are a result of altered signaling from heterotypic rather from homotypic Eph clusters.

scholarly journals Ectopic EphA4 Receptor Induces Posterior Protrusions via FGF Signaling in Xenopus Embryos

2004 ◽  
Vol 15 (4) ◽  
pp. 1647-1655 ◽  
Author(s):  
Eui Kyun Park ◽  
Neil Warner ◽  
Yong-Sik Bong ◽  
David Stapleton ◽  
Ryu Maeda ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Sh2 Domain ◽  
Binding Motif ◽  
Eph Receptors ◽  
Fgf Signaling ◽  
Wild Type ◽  
Sam Domain ◽  
Xenopus Embryos

The Eph family of receptor tyrosine kinases regulates numerous biological processes. To examine the biochemical and developmental contributions of specific structural motifs within Eph receptors, wild-type or mutant forms of the EphA4 receptor were ectopically expressed in developing Xenopus embryos. Wild-type EphA4 and a mutant lacking both the SAM domain and PDZ binding motif were constitutively tyrosine phosphorylated in vivo and catalytically active in vitro. EphA4 induced loss of cell adhesion, ventro-lateral protrusions, and severely expanded posterior structures in Xenopus embryos. Moreover, mutation of a conserved SAM domain tyrosine to phenylalanine (Y928F) enhanced the ability of EphA4 to induce these phenotypes, suggesting that the SAM domain may negatively regulate some aspects of EphA4 activity in Xenopus. Analysis of double mutants revealed that the Y928F EphA4 phenotypes were dependent on kinase activity; juxtamembrane sites of tyrosine phosphorylation and SH2 domain-binding were required for cell dissociation, but not for posterior protrusions. The induction of protrusions and expansion of posterior structures is similar to phenotypic effects observed in Xenopus embryos expressing activated FGFR1. Furthermore, the budding ectopic protrusions induced by EphA4 express FGF-8, FGFR1, and FGFR4a. In addition, antisense morpholino oligonucleotide-mediated loss of FGF-8 expression in vivo substantially reduced the phenotypic effects in EphA4Y928F expressing embryos, suggesting a connection between Eph and FGF signaling.

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