Cell communication systems based on polypeptide ligands use transmembrane receptors to transmit signals across the plasma membrane. In their biogenesis, receptors depend on the endoplasmic reticulum (ER)-Golgi system for folding, maturation, transport and localization to the cell surface. ER stress, caused by protein overproduction and misfolding, is a well-known pathology in neurodegeneration, cancer and numerous other diseases. How ER stress affects cell communication via transmembrane receptors is largely unknown. In disease models of multiple myeloma, chronic lymphocytic leukemia and osteogenesis imperfecta, we show that ER stress leads to loss of the mature transmembrane receptors FGFR3, ROR1, FGFR1, LRP6, FZD5 and PTH1R at the cell surface, resulting in impaired downstream signaling. This is caused by downregulation of receptor production and increased intracellular retention of immature receptor forms. Reduction of ER stress by treatment of cells with the chemical chaperone tauroursodeoxycholic acid or by expression of the chaperone protein BiP resulted in restoration of receptor maturation and signaling. We show a previously unappreciated pathological effect of ER stress; impaired cellular communication due to altered receptor processing. Our findings have implications for disease mechanisms related to ER stress and are particularly important when receptor-based pharmacological approaches are used for treatment.

• Klíčová slova
• ER, Endoplasmic reticulum, Impaired, Receptor, Signaling, Stress, Transmembrane,
• MeSH
• chaperon endoplazmatického retikula BiP MeSH
• kyselina taurochenodeoxycholová farmakologie   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• receptory buněčného povrchu * metabolismus   MeSH
• signální transdukce * účinky léků   MeSH
• stres endoplazmatického retikula * účinky léků   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chaperon endoplazmatického retikula BiP MeSH
• kyselina taurochenodeoxycholová MeSH
• receptory buněčného povrchu * MeSH
• ursodoxicoltaurine MeSH Prohlížeč

Impaired fibroblast growth factor receptor (FGFR) signaling is associated with many human conditions, including growth disorders, degenerative diseases, and cancer. Current FGFR therapeutics are based on chemical inhibitors of FGFR tyrosine kinase activity (TKIs). However, FGFR TKIs are limited in their target specificity as they generally inhibit all FGFRs and other receptor tyrosine kinases. In the search for specific inhibitors of human FGFR1, we identified VZ23, a DNA aptamer that binds to FGFR1b and FGFR1c with a KD of 55 nM and 162 nM, respectively, but not to the other FGFR variants (FGFR2b, FGFR2c, FGFR3b, FGFR3c, FGFR4). In cells, VZ23 inhibited the activation of downstream FGFR1 signaling and FGFR1-mediated regulation of cellular senescence, proliferation, and extracellular matrix homeostasis. Consistent with the specificity toward FGFR1 observed in vitro, VZ23 did not inhibit FGFR2-4 signaling in cells. We show that the VZ23 inhibits FGFR1 signaling in the presence of cognate fibroblast growth factor (FGF) ligands and its inhibitory activity is linked to its capacity to form unusual G-quadruplex structure. Our data suggest that targeting FGFR1 with DNA aptamers could be an effective alternative to TKIs for treating impaired FGFR1 signaling in human craniosynostoses.

• Klíčová slova
• DNA aptamer, FGFR signaling, FGFR1, MT: Oligonucleotides: Therapies and Applications, craniosynostosis, extracellular domain, inhibitor, skeletal dysplasia,
• Publikační typ
• časopisecké články MeSH

Achondroplasia is the most common form of human dwarfism caused by mutations in the FGFR3 receptor tyrosine kinase. Current therapy begins at 2 years of age and improves longitudinal growth but does not address the cranial malformations including midface hypoplasia and foramen magnum stenosis, which lead to significant otolaryngeal and neurologic compromise. A recent clinical trial found partial restoration of cranial defects with therapy starting at 3 months of age, but results are still inconclusive. The benefits of achondroplasia therapy are therefore controversial, increasing skepticism among the medical community and patients. We used a mouse model of achondroplasia to test treatment protocols aligned with human studies. Early postnatal treatment (from day 1) was compared with late postnatal treatment (from day 4, equivalent to ~5 months in humans). Animals were treated with the FGFR3 inhibitor infigratinib and the effect on skeleton was thoroughly examined. We show that premature fusion of the skull base synchondroses occurs immediately after birth and leads to defective cranial development and foramen magnum stenosis in the mouse model to achondroplasia. This phenotype appears significantly restored by early infigratinib administration when compared with late treatment, which provides weak to no rescue. In contrast, the long bone growth is similarly improved by both early and late protocols. We provide clear evidence that immediate postnatal therapy is critical for normalization of skeletal growth in both the cranial base and long bones and the prevention of sequelae associated with achondroplasia. We also describe the limitations of early postnatal therapy, providing a paradigm-shifting argument for the development of prenatal therapy for achondroplasia.

The article provides clear evidence that achondroplasia should be treated immediately after birth, not only to increase height (appendicular growth), but more importantly to prevent defective cranial skeletogenesis and associated severe neurological complications. Although later treatment promotes growth of the long bones (achondroplasia patients grow taller), the defective head skeleton that forms before and/or early after birth cannot be restored if therapy is not started immediately after birth. We also describe the limitations of postnatal treatment and make a strong case for the development of prenatal therapy for achondroplasia, which appears necessary for a comprehensive treatment of this condition.

• Klíčová slova
• Fgfr3, achondroplasia, fibroblast growth factor, infigratinib, postnatal, treatment,
• MeSH
• achondroplazie * patologie   farmakoterapie   MeSH
• lebka patologie   účinky léků   MeSH
• lidé MeSH
• modely nemocí na zvířatech * MeSH
• myši MeSH
• receptor fibroblastových růstových faktorů, typ 3 * genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• receptor fibroblastových růstových faktorů, typ 3 * MeSH

The FGF system is the most complex of all receptor tyrosine kinase signaling networks with 18 FGF ligands and four FGFRs that deliver morphogenic signals to pattern most embryonic structures. Even when a single FGFR is expressed in the tissue, different FGFs can trigger dramatically different biological responses via this receptor. Here we show both quantitative and qualitative differences in the signaling of one of the FGF receptors, FGFR1c, in response to different FGFs. We provide an overview of the recent discovery that FGFs engage in biased signaling via FGFR1c. We discuss the concept of ligand bias, which represents qualitative differences in signaling as it is a measure of differential ligand preferences for different downstream responses. We show how FGF ligand bias manifests in functional data in cultured chondrocyte cells. We argue that FGF-ligand bias contributes substantially to FGF-driven developmental processes, along with known differences in FGF expression levels, FGF-FGFR binding coefficients and differences in FGF stability in vivo.

• Klíčová slova
• Bias, FGF, FGFR, Signaling,
• MeSH
• chondrocyty metabolismus   MeSH
• fibroblastové růstové faktory * metabolismus   MeSH
• lidé MeSH
• ligandy MeSH
• receptor fibroblastových růstových faktorů, typ 1 * metabolismus   MeSH
• receptory fibroblastových růstových faktorů * metabolismus   MeSH
• signální transdukce * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• fibroblastové růstové faktory * MeSH
• ligandy MeSH
• receptor fibroblastových růstových faktorů, typ 1 * MeSH
• receptory fibroblastových růstových faktorů * MeSH

The differential signaling of multiple FGF ligands through a single fibroblast growth factor (FGF) receptor (FGFR) plays an important role in embryonic development. Here, we use quantitative biophysical tools to uncover the mechanism behind differences in FGFR1c signaling in response to FGF4, FGF8, and FGF9, a process which is relevant for limb bud outgrowth. We find that FGF8 preferentially induces FRS2 phosphorylation and extracellular matrix loss, while FGF4 and FGF9 preferentially induce FGFR1c phosphorylation and cell growth arrest. Thus, we demonstrate that FGF8 is a biased FGFR1c ligand, as compared to FGF4 and FGF9. Förster resonance energy transfer experiments reveal a correlation between biased signaling and the conformation of the FGFR1c transmembrane domain dimer. Our findings expand the mechanistic understanding of FGF signaling during development and bring the poorly understood concept of receptor tyrosine kinase ligand bias into the spotlight.

• Klíčová slova
• FGFR, biased signaling, molecular biophysics, none, signal transduction, structural biology,
• MeSH
• fibroblastové růstové faktory * MeSH
• fosforylace MeSH
• lidé MeSH
• ligandy MeSH
• receptor fibroblastových růstových faktorů, typ 1 genetika   MeSH
• signální transdukce * MeSH
• těhotenství MeSH
• zkreslení výsledků (epidemiologie) MeSH
• Check Tag
• lidé MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• FGFR1 protein, human MeSH Prohlížeč
• fibroblastové růstové faktory * MeSH
• ligandy MeSH
• receptor fibroblastových růstových faktorů, typ 1 MeSH