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Corticotropin-(1--24)-tetracosapeptide affects protein phosphorylation and polyphosphoinositide metabolism in rat brain.

ABSTRACT: 1. Effects of corticotropin-(1--24)-tetracosapeptide on the endogenous phosphorylation of proteins and lipids were studied in a membrane/cytosol fraction prepared from a lysed crude mitochondrial/synaptosomal fraction. 2. The labelling of proteins and lipids was monitored by incubation of the subcellular fraction for 10s with [gamma-32P]ATP. 3. The phosphorylation of proteins was dose-dependently inhibited by the peptide (40% of control incubations at 100 microM-corticotropin). 4. Of the membrane phospholipids only phosphatidylinositol phosphate, phosphatidylinositol bisphosphate and phosphatidic acid became labelled. Corticotropin dose-dependently increased the formation of phosphatidylinositol bisphosphate and inhibited the production of phosphatidic acid (470% and 50% respectively of control incubations, at 100 microM of the peptide) and had no effect on phosphatidylinositol phosphate. 5. Phosphatase activity was observed to act on phosphatidylinositol bisphosphate, phosphatidylinositol phosphate and phosphoprotein but not on phosphatidic acid. 6. Corticotropin interacted with the kinases rather than with the phosphatases. 7. The formation of phosphatidylinositol bisphosphate and phosphatidic acid was maximal at 1--10mM-Mg2+ in the absence of Ca2+, and the production of phosphatidylinositol phosphate was maximal at 30mM-Mg2+. 8. The basal value of lipid phosphorylation decreased with increasing Ca2+ concentration. 9. Ca2+ abolished the effect of corticotropin on phosphatidylinositol bisphosphate formation (470%, 190% and 100% of control incubations at respectively 0, 0.1 and 1 mM-Ca2+). 10. The data provide evidence that the effects of corticotropin on protein phosphorylation and on polyphosphoinositide metabolism in brain membranes are related.

SUBMITTER: Jolles J

PROVIDER: S-EPMC1162742 | biostudies-other | 1981 Jan

REPOSITORIES: biostudies-other

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Project description:BackgroundThe DHTKD1-encoded 2-oxoadipate dehydrogenase (OADH) oxidizes 2-oxoadipate-a common intermediate of the lysine and tryptophan catabolism. The mostly low and cell-specific flux through these pathways, and similar activities of OADH and ubiquitously expressed 2-oxoglutarate dehydrogenase (OGDH), agree with often asymptomatic phenotypes of heterozygous mutations in the DHTKD1 gene. Nevertheless, OADH/DHTKD1 are linked to impaired insulin sensitivity, cardiovascular disease risks, and Charcot-Marie-Tooth neuropathy. We hypothesize that systemic significance of OADH relies on its generation of glutaryl residues for protein glutarylation. Using pharmacological inhibition of OADH and the animal model of spinal cord injury (SCI), we explore this hypothesis.MethodsThe weight-drop model of SCI, a single intranasal administration of an OADH-directed inhibitor trimethyl adipoyl phosphonate (TMAP), and quantification of the associated metabolic changes in the rat brain employ established methods.ResultsThe TMAP-induced metabolic changes in the brain of the control, laminectomized (LE) and SCI rats are long-term and (patho)physiology-dependent. Increased glutarylation of the brain proteins, proportional to OADH expression in the control and LE rats, represents a long-term consequence of the OADH inhibition. The proportionality suggests autoglutarylation of OADH, supported by our mass-spectrometric identification of glutarylated K155 and K818 in recombinant human OADH. In SCI rats, TMAP increases glutarylation of the brain proteins more than OADH expression, inducing a strong perturbation in the brain glutathione metabolism. The redox metabolism is not perturbed by TMAP in LE animals, where the inhibition of OADH increases expression of deglutarylase sirtuin 5. The results reveal the glutarylation-imposed control of the brain glutathione metabolism. Glutarylation of the ODP2 subunit of pyruvate dehydrogenase complex at K451 is detected in the rat brain, linking the OADH function to the brain glucose oxidation essential for the redox state. Short-term inhibition of OADH by TMAP administration manifests in increased levels of tryptophan and decreased levels of sirtuins 5 and 3 in the brain.ConclusionPharmacological inhibition of OADH affects acylation system of the brain, causing long-term, (patho)physiology-dependent changes in the expression of OADH and sirtuin 5, protein glutarylation and glutathione metabolism. The identified glutarylation of ODP2 subunit of pyruvate dehydrogenase complex provides a molecular mechanism of the OADH association with diabetes.

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Corticotropin-(1--24)-tetracosapeptide affects protein phosphorylation and polyphosphoinositide metabolism in rat brain.

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