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Träfflista för sökning "WFRF:(Frikha Fakher) "

Search: WFRF:(Frikha Fakher)

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1.
  • Aifa, Sami, et al. (author)
  • Phosphorylation of Thr654 but not Thr669 within the juxtamembrane domain of the EGF receptor inhibits calmodulin binding
  • 2006
  • In: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 347:2, s. 381-387
  • Journal article (peer-reviewed)abstract
    • Calcium-calmodulin (CaM) binding to the epidermal growth factor receptor (EGFR) has been shown to both inhibit and stimulate receptor activity. CaM binds to the intracellular juxtamembrane (JM) domain (Met645-Phe688) of EGFR. Protein kinase C (PKC) mediated phosphorylation of Thr654 occurs within this domain. CaM binding to the JM domain inhibits PKC phosphorylation and conversely PKC mediated phosphorylation of Thr654 or Glu substitution of Thr654 inhibits CaM binding. A second threonine residue (Thr669) within the JM domain is phosphorylated by the mitogen-activated protein kinase (MAPK). Previous results have shown that CaM interferes with EGFR-induced MAPK activation. If and how phosphorylation of Thr669 affects CaM-EGFR interaction is however not known.In the present study we have used surface plasmon resonance (BIAcore) to study the influence of Thr669 phosphorylation on real time interactions between the intracellular juxtamembrane (JM) domain of EGFR and CaM. The EGFR-JM was expressed as GST fusion proteins in Escherichia coli and phosphorylation was mimicked by generating Glu substitutions of either Thr654 or Thr669. Purified proteins were coupled to immobilized anti-GST antibodies at the sensor surface and increasing concentration of CaM was applied. When mutating Thr654 to Glu654 no specific CaM binding could be detected. However, neither single substitutions of Thr669 (Gly669 or Glu669) nor double mutants Gly654/Gly669 or Gly654/Glu669 influenced the binding of CaM to the EGFR-JM. This clearly shows that PKC may regulate EGF-mediated CaM signalling through phosphorylation of Thr654 whereas phosphorylation of Thr669 seems to play a CaM independent regulatory role. The role of both residues in the EGFR-calmodulin interaction was also studied in silico. Our modelling work supports a scenario where Thr654 from the JM domain interacts with Glu120 in the calmodulin molecule. Phosphorylation of Thr654 or Glu654 substitution creates a repulsive electrostatic force that would diminish CaM binding to the JM domain. These results are in line with the Biacore experiments showing a weak binding of the CaM to the JM domain with Thr654 mutated to Glu. Furthermore, these results provide a hypothesis to how CaM binding to EGFR might both positively and negatively interfere with EGFR-activity. © 2006 Elsevier Inc. All rights reserved.
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2.
  • Tababi, Mouna, et al. (author)
  • Domain landscapes of somatic NF1 mutations in pheochromocytoma and paraganglioma
  • 2023
  • In: Gene. - : ELSEVIER. - 0378-1119 .- 1879-0038. ; 872
  • Journal article (peer-reviewed)abstract
    • Pheochromocytoma and paraganglioma (PPGL), are rare neuroendocrine tumors arising from the adrenal me-dulla and extra-adrenal paraganglia, respectively. Up to about 60% are explained by germline or somatic mu-tations in one of the major known susceptibility genes e.g., in NF1, RET, VHL, SDHx, MAX and HRAS. Targeted Next Generation Sequencing was performed in 14 sporadic tumors using a panel including 26 susceptibility genes to characterize the mutation profile. A total of 6 germline and 8 somatic variants were identified. The most frequent somatic mutations were found in NF1 (36%), four have not been reported earlier in PCC or PGL. Gene expression profile analysis showed that NF1 mutated tumors are classified into RTK3 subtype, cluster 2, with a high expression of genes associated with chromaffin cell differentiation, and into a RTK2 subtype, cluster 2, as well with overexpression of genes associated with cortisol biosynthesis. On the other hand, by analyzing the entire probe set on the array and TCGA data, ALDOC was found as the most significantly down regulated gene in NF1-mutated tumors compared to NF1-wild-type. Differential gene expression analysis showed a significant difference between Nt -and Ct-NF1 domains in mutated tumors probably engaging different cellular pathways. Notably, we had a metastatic PCC with a Ct-NF1 frameshift mutation and when performing protein docking analysis, Ct-NF1 showed an interaction with Nt-FAK suggesting their involvement in cell adhesion and cell growth. These results show that depending on the location of the NF1-mutation different pathways are activated in PPGLs. Further studies are required to clarify their clinical significance.
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