The Eph receptor tyrosine kinases and their ephrin ligands regulate many physiological and pathological processes. EphA4 plays important roles in nervous system development and adult homeostasis, while aberrant EphA4 signaling has been implicated in neurodegeneration. EphA4 may also affect cancer malignancy, but the regulation and effects of EphA4 signaling in cancer are poorly understood. A correlation between decreased patient survival and high EphA4 mRNA expression in melanoma tumors that also highly express ephrinA ligands suggests that enhanced EphA4 signaling may contribute to melanoma progression. A search for EphA4 gain-of-function mutations in melanoma uncovered a mutation of the highly conserved leucine 920 in the EphA4 sterile alpha motif (SAM) domain. We found that mutation of L920 to phenylalanine (L920F) potentiates EphA4 autophosphorylation and signaling, making it the first documented EphA4 cancer mutation that increases kinase activity. Quantitative Föster resonance energy transfer and fluorescence intensity fluctuation (FIF) analyses revealed that the L920F mutation induces a switch in EphA4 oligomer size, from a dimer to a trimer. We propose this switch in oligomer size as a novel mechanism underlying EphA4-linked tumorigenesis. Molecular dynamics simulations suggest that the L920F mutation alters EphA4 SAM domain conformation, leading to the formation of EphA4 trimers that assemble through two aberrant SAM domain interfaces. Accordingly, EphA4 wild-type and the L920F mutant are affected differently by the SAM domain and are differentially regulated by ephrin ligand stimulation. The increased EphA4 activation induced by the L920F mutation, through the novel mechanism we uncovered, supports a functional role for EphA4 in promoting pathogenesis.
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http://dx.doi.org/10.1016/j.jbc.2021.100876 | DOI Listing |
J Biol Chem
December 2024
Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, United States. Electronic address:
Missense mutations in the EPHA1 receptor tyrosine kinase have been identified in Alzheimer's patients. To gain insight into their potential role in disease pathogenesis, we investigated the effects of four of these mutations. We show that the P460L mutation in the second fibronectin type III (FN2) domain drastically reduces EPHA1 cell surface localization while increasing tyrosine phosphorylation of the cell surface localized receptor.
View Article and Find Full Text PDFScience
December 2024
Department of Immunology, University of Washington, Seattle, WA.
Antiviral signaling downstream of RIG-I-like receptors (RLRs) proceeds through a multi-protein complex organized around the adaptor protein mitochondrial antiviral signaling protein (MAVS). Protein complex function can be modulated by RNA molecules that provide allosteric regulation or act as molecular guides or scaffolds. We hypothesized that RNA plays a role in organizing MAVS signaling platforms.
View Article and Find Full Text PDFJ Nanobiotechnology
December 2024
Precirix, Burg. Etienne Demunterlaan 3, Brussels, Matthias, B-1090, Belgium.
Background: Folate receptor alpha (FRα) overexpression is seen in many cancers. Radioligand therapy (RLT) has emerged as a promising tool to target FRα and has been investigated previously, but further progression was limited due to high kidney retention and, subsequently, toxicity. To circumvent this, we present here the development of a [I]I-GMIB-conjugated anti-human FRα (hFRα) single-domain antibody (sdAb), with intrinsically fast renal clearance and concomitant low kidney retention.
View Article and Find Full Text PDFCell Death Dis
December 2024
Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt, Germany.
The concept of Targeted Protein Degradation (TPD) has been introduced as an attractive alternative to the development of classical inhibitors. TPD can extend the range of proteins that can be pharmacologically targeted beyond the classical targets for small molecule inhibitors, as a binding pocket is required but its occupancy does not need to lead to inhibition. The method is based on either small molecules that simultaneously bind to a protein of interest and to a cellular E3 ligase and bring them in close proximity (molecular glue) or a bi-functional molecule synthesized from the chemical linkage of a target protein-specific small molecule and one that binds to an E3 ligase (Proteolysis Targeting Chimeras (PROTAC)).
View Article and Find Full Text PDFFEBS J
December 2024
Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, China.
Calcium/calmodulin-dependent serine protein kinase (CASK) interaction protein 1/2 (Caskin1/2) is essential neuronal synaptic scaffold protein in nervous system development. Knockouts of Caskin1/2 display severe deficits in novelty recognition and spatial memory. The tandem sterile alpha motif (SAM) domains of Caskin1/2, also conserved in their Drosophila homolog Ckn, are known to form homopolymers, yet their dynamic regulation mechanism remains unclear.
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