Fibroblast growth factor receptor 1

Fibroblast growth factor receptor 1 (FGFR1), also known as basic fibroblast growth factor receptor 1, fms-related tyrosine kinase-2 / Pfeiffer syndrome, and

Activation of the gamma isoforms of

Recent publication on the 2.5 Å crystal structure of PLCγ in complex with FGFR1 kinase (PDB: 3GQI) provides new insights in understanding the molecular mechanism of FGFR1's recruitment of PLCγ by its SH2 domains. Figure 1 on the extreme right shows the PLCγ-FGFR1 kinase complex with the c-SH2 domain colored in red, n-SH2 domain colored in blue, and the interdomain linker colored in yellow. The structure contains typical SH2 domain, with two α-helices and three antiparallel β-strands in each SH2 domain. In this complex, the phosphorylated tyrosine (pY766) on the C-terminal tail of FGFR1 kinase binds preferentially to the nSH2 domain of PLCγ. The phosphorylation of tyrosine residue 766 on FGFR1 kinase forms hydrogen bonds with the n-SH2 to stabilize the complex. Hydrogen bonds in the binding pocket help to stabilize the PLCγ-FGFR1 kinase complex. The water molecule as shown mediates the interaction of asparagine 647 (N647) and aspartate 768 (D768) to further increase the binding affinity of the n-SH2 and FGFR1 kinase complex. (Figure 2). The phosphorylation of tyrosine 653 and tyrosine 654 in the active kinase conformation causes a large conformation change in the activation segment of FGFR1 kinase. Threonine 658 is moved by 24Å from the inactive form (Figure 3.) to the activated form of FGFR1 kinase (Figure 4.). The movement causes the closed conformation in the inactive form to open to enable substrate binding. It also allows the open conformation to coordinate Mg2+ with AMP-PCP (analog of ATP). In addition, pY653 and pY654 in the active form helps to maintain the open conformation of the SH2 and FGFR1 kinase complex. However, the mechanism by which the phosphorylation at Y653 and Y654 helps to recruit the SH2 domain to its C-terminal tail upon phosphorylation of Y766 remains elusive. Figure 5 shows the overlay structure of active and inactive forms of FGFR1 kinase. Figure 6 shows the dots and contacts on phosphorylated tyrosine residues 653 and 654. Green dots show highly favorable contacts between pY653 and pY654 with surrounding residues. Red spikes show unfavorable contacts in the activation segment. The figure is generated through Molprobity extension on Pymol.

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  Figure 2. Hydrogen bonds at pY766
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  Figure 3. Closed conformation in Inactive FRFR1 kinase
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  Figure 4. Open conformation in active FRFR1 kinase
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  Figure 5. Overlay Structures of Active and Inactive Forms of FGFR1 kinase
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  Figure 6. Dots and contacts on pY653 & pY654
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  Figure 7. The β-factor of the PLC-FGFR1 kinase complex

The tyrosine kinase region of FGFR1 binds to the N-SH2 domain of PLCγ primarily through charged amino acids. Arginine residue (R609) on the N-SH2 domain forms a salt bridge to aspartate 755 (D755) on the FGFR1 domain. The acid base pairs located in the middle of the interface are nearly parallel to each other, indicating a highly favorable interaction. The N-SH2 domain makes an additional polar contact through water-mediated interaction that takes place between the N-SH2 domain and the FGFR1 kinase region. The arginine residue 609 (R609) on the FGFR1 kinase also forms a salt bridge to the aspartate residue (D594) on the N-SH2 domain. The acid-base pair interacts with each other carry out a reduction–oxidation reaction that stabilizes the complex (Figure 7). Previous studies have done to elucidate the binding affinity of the n-SH2 domain with the FGFR1 kinase complex by mutating these phenylalanine or valine amino acids. The results from isothermal titration calorimetry indicated that the binding affinity of the complex decreased by 3 to 6-fold, without affecting the phosphorylation of the tyrosine residues.^[12]

Cell inhibition

FGF-induced activation of FGFR1 also stimulates the activation of

Somatic mutations and epigenetic changes in the expression of the FGFR1 gene occur in and are thought to contribute to various types of lung, breast, hematological, and other types of cancers.

Lung cancers

Amplification of FGFR1 also occurs in ~10% of estrogen receptor positive breast cancers, particularly of the luminal subtype B form of breast cancer. The presence of FGFR1 amplification has been correlated with resistance to hormone blocking therapy and found to be a poor prognostic factor in the disease.^[9][10]

Hematological cancers

In certain rare hematological cancers, the