title: Structural basis for the allosteric inhibitory mechanism of human kidney-type glutaminase (KGA) and its regulation by Raf-Mek-Erk signaling in cancer cell metabolism.
abstract: Besides thriving on altered glucose metabolism, cancer cells undergo glutaminolysis to meet their energy demands. As the first enzyme in catalyzing glutaminolysis, human kidney-type glutaminase isoform (KGA) is becoming an attractive target for small molecules such as BPTES [bis-2-(5 phenylacetamido-1, 2, 4-thiadiazol-2-yl) ethyl sulfide], although the regulatory mechanism of KGA remains unknown. On the basis of crystal structures, we reveal that BPTES binds to an allosteric pocket at the dimer interface of KGA, triggering a dramatic conformational change of the key loop (Glu312-Pro329) near the catalytic site and rendering it inactive. The binding mode of BPTES on the hydrophobic pocket explains its specificity to KGA. Interestingly, KGA activity in cells is stimulated by EGF, and KGA associates with all three kinase components of the Raf-1/Mek2/Erk signaling module. However, the enhanced activity is abrogated by kinase-dead, dominant negative mutants of Raf-1 (Raf-1-K375M) and Mek2 (Mek2-K101A), protein phosphatase PP2A, and Mek-inhibitor U0126, indicative of phosphorylation-dependent regulation. Furthermore, treating cells that coexpressed Mek2-K101A and KGA with suboptimal level of BPTES leads to synergistic inhibition on cell proliferation. Consequently, mutating the crucial hydrophobic residues at this key loop abrogates KGA activity and cell proliferation, despite the binding of constitutive active Mek2-S222/226D. These studies therefore offer insights into (i) allosteric inhibition of KGA by BPTES, revealing the dynamic nature of KGA's active and inhibitory sites, and (ii) cross-talk and regulation of KGA activities by EGF-mediated Raf-Mek-Erk signaling. These findings will help in the design of better inhibitors and strategies for the treatment of cancers addicted with glutamine metabolism.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543.
authors.forename: K
authors.initials: K
authors.lastname: Thangavelu
authors.forename: Catherine Qiurong
authors.initials: CQ
authors.lastname: Pan
authors.forename: Tobias
authors.initials: T
authors.lastname: Karlberg
authors.forename: Ganapathy
authors.initials: G
authors.lastname: Balaji
authors.forename: Mahesh
authors.initials: M
authors.lastname: Uttamchandani
authors.forename: Valiyaveettil
authors.initials: V
authors.lastname: Suresh
authors.forename: Herwig
authors.initials: H
authors.lastname: Schüler
authors.forename: Boon Chuan
authors.initials: BC
authors.lastname: Low
authors.forename: J
authors.initials: J
authors.lastname: Sivaraman
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003461:Crystallography; D005972:Glutaminase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000201:enzymology*; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000235:genetics; D020935:MAP Kinase Signaling System / Q000502:physiology; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013440:Sulfides / Q000378:metabolism* / Q000494:pharmacology; D013830:Thiadiazoles / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D013440:Sulfides; D013830:Thiadiazoles; C523193:bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide; C482128:MAP2K2 protein, human; D019908:Proto-Oncogene Proteins c-raf; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D005972:Glutaminase