Proteomic and Metabolic Analyses of S49 Lymphoma Cells Reveal Novel Regulation of Mitochondria by cAMP and Protein Kinase A

Abstract

Cyclic AMP (cAMP), acting via protein kinase A (PKA), regulates many cellular responses, but the role of mitochondria in such responses is poorly understood. To define such roles, we used quantitative proteomic analysis of mitochondria-enriched fractions and performed functional and morphologic studies of wild-type (WT) and kin(-) (PKA-null) murine S49 lymphoma cells. Basally, 75 proteins significantly differed in abundance between WT and kin(-) S49 cells. WT, but not kin(-), S49 cells incubated with the cAMP analog 8-(4-chlorophenylthio)adenosine cAMP (CPT-cAMP) for 16 h have (a) increased expression of mitochondria-related genes and proteins, including ones in pathways of branched-chain amino acid and fatty acid metabolism and (b) increased maximal capacity of respiration on branched-chain keto acids and fatty acids. CPT-cAMP also regulates the cellular rate of ATP-utilization, as the rates of both ATP-linked respiration and proton efflux are decreased in WT but not kin(-) cells. CPT-cAMP protected WT S49 cells from glucose or glutamine deprivation, In contrast, CPT-cAMP did not protect kin(-) cells or WT cells treated with the PKA inhibitor H89 from glutamine deprivation. Under basal conditions, the mitochondrial structure of WT and kin(-) S49 cells is similar. Treatment with CPT-cAMP produced apoptotic changes (i.e. decreased mitochondrial density and size and loss of cristae) in WT, but not kin(-) cells. Together, these findings show that cAMP acts via PKA to regulate multiple aspects of mitochondrial function and structure. Mitochondrial perturbation thus likely contributes to cAMP/PKA-mediated cellular responses.

Keywords: cell metabolism; cyclic AMP (cAMP); mitochondria; protein kinase A (PKA); proteomics.