A redox-active switch in fructosamine-3-kinases expands the regulatory repertoire of the protein kinase superfamily

Abstract

<jats:p>Aberrant regulation of metabolic kinases by altered redox homeostasis substantially contributes to aging and various diseases, such as diabetes. We found that the catalytic activity of a conserved family of fructosamine-3-kinases (FN3Ks), which are evolutionarily related to eukaryotic protein kinases, is regulated by redox-sensitive cysteine residues in the kinase domain. The crystal structure of the FN3K homolog from <jats:italic>Arabidopsis thaliana</jats:italic> revealed that it forms an unexpected strand-exchange dimer in which the ATP-binding P-loop and adjoining β strands are swapped between two chains in the dimer. This dimeric configuration is characterized by strained interchain disulfide bonds that stabilize the P-loop in an extended conformation. Mutational analysis and solution studies confirmed that the strained disulfides function as redox “switches” to reversibly regulate the activity and dimerization of FN3K. Human FN3K, which contains an equivalent P-loop Cys, was also redox sensitive, whereas ancestral bacterial FN3K homologs, which lack a P-loop Cys, were not. Furthermore, CRISPR-mediated knockout of FN3K in human liver cancer cells altered the abundance of redox metabolites, including an increase in glutathione. We propose that redox regulation evolved in FN3K homologs in response to changing cellular redox conditions. Our findings provide insights into the origin and evolution of redox regulation in the protein kinase superfamily and may open new avenues for targeting human FN3K in diabetic complications.</jats:p>

The Taming of Nuclear Factor Erythroid-2-Related Factor-2 (Nrf2) Deglycation by Fructosamine-3-Kinase (FN3K)-Inhibitors-A Novel Strategy to Combat Cancers

“…FN3K is highly conserved across various living beings to maintain cellular homeostasis by mitigating AGE-mediated oxidative stress [ 161 ]. Prospective research should focus on uncovering the fundamental role and regulation of FN3K in several cellular functions and disease models [ 162 ]. FN3K is more abundantly found in the liver, heart, kidney, brain, and skeletal muscles and relatively higher in erythrocytes [ 158 ].…”

“…The functional aspects of FN3K exclusively rely on its conserved structural motifs in this protein. For instance, the redox-sensitive P-loop Cys is highly conserved amongst FN3K orthologs in both prokaryotes and eukaryotes [ 162 ]. The efficient catalysis of FN3K in delgycating the glycated proteins depends on the P-loop, which mainly consists of a GlyxGlyxxGly motif.…”

“…The efficient catalysis of FN3K in delgycating the glycated proteins depends on the P-loop, which mainly consists of a GlyxGlyxxGly motif. This motif is primarily conserved in diverse ATP enzymes to foster conformational flexibility during catalysis [ 162 ]. A report by Safal Shrestha et al (2020) delineated that FN3K is composed of Gly residues, as well as Cys residues, in the P-loop.…”

“…A report by Safal Shrestha et al (2020) delineated that FN3K is composed of Gly residues, as well as Cys residues, in the P-loop. The authors of this study reported that tyrosine protein kinases were also composed of conserved Cys residues similar to FN3K in the Gly-rich motifs of P-loop [ 162 ]. For example, the presence of Cys at the position Cys32 of FN3K can be observed in the tyrosine kinases of eukaryotes, viz., SRC, FGFR (human fibroblast growth factor receptor), YES1 (YES proto-oncogene 1), and FYN tyrosine kinases [ 162 ].…”

“…The authors of this study reported that tyrosine protein kinases were also composed of conserved Cys residues similar to FN3K in the Gly-rich motifs of P-loop [ 162 ]. For example, the presence of Cys at the position Cys32 of FN3K can be observed in the tyrosine kinases of eukaryotes, viz., SRC, FGFR (human fibroblast growth factor receptor), YES1 (YES proto-oncogene 1), and FYN tyrosine kinases [ 162 ]. The expression of both FN3K and FN3K-RP with Cys-rich motifs is highly abundant in human tumors [ 162 ].…”