Two structurally distinct and spatially compartmentalized adenylate kinases are expressed from the AK1 gene in mouse brain.

Contains fulltext : 59150.pdf (publisher's version ) (Closed access)Adenylate kinases (AK, EC 2.7.4.3) have been considered important enzymes for energy homeostasis and metabolic signaling. To gain a better understanding of their cell-specific significance we studied the structural and functional aspects of products of one adenylate kinase gene, AK1, in mouse tissues. By combined computer database comparison and Northern analysis of mRNAs, we identified transcripts of 0.7 and 2.0 kilobases with different 5' and 3' non-coding regions which result from alternative use of promoters and polyadenylation sites. These mRNAs specify two distinct proteins, AK1 and a membrane-bound AK1 isoform (AK1beta), which differ in their N-terminal end and are co-expressed in several tissues with high-energy demand, including the brain. Immunohistochemical analysis of brain tissue and primary neurons and astrocytes in culture demonstrated that AK1 isoforms are expressed predominantly in neurons. AK1beta, when tested in transfected COS-1 and N2a neuroblastoma cells, located at the cellular membrane and was able to catalyze phosphorylation of ADP in vitro. In addition, AK1beta mediated AMP-induced activation of recombinant ATP-sensitive potassium channels in the presence of ATP. Thus, two structurally distinct AK1 isoforms co-exist in the mouse brain within distinct cellular locations. These enzymes may function in promoting energy homeostasis in the compartmentalized cytosol and in translating cellular energetic signals to membrane metabolic sensors

Coupling of cell energetics with membrane metabolic sensing. Integrative signaling through creatine kinase phosphotransfer disrupted by M-CK gene knock-out.

Transduction of metabolic signals is essential in preserving cellular homeostasis. Yet, principles governing integration and synchronization of membrane metabolic sensors with cell metabolism remain elusive. Here, analysis of cellular nucleotide fluxes and nucleotide-dependent gating of the ATP-sensitive K+ (K(ATP)) channel, a prototypic metabolic sensor, revealed a diffusional barrier within the submembrane space, preventing direct reception of cytosolic signals. Creatine kinase phosphotransfer, captured by 18O-assisted 31P NMR, coordinated tightly with ATP turnover, reflecting the cellular energetic status. The dynamics of high energy phosphoryl transfer through the creatine kinase relay permitted a high fidelity transmission of energetic signals into the submembrane compartment synchronizing K(ATP) channel activity with cell metabolism. Knock-out of the creatine kinase M-CK gene disrupted signal delivery to K(ATP) channels and generated a cellular phenotype with increased electrical vulnerability. Thus, in the compartmentalized cell environment, phosphotransfer systems shunt diffusional barriers and secure regimented signal transduction integrating metabolic sensors with the cellular energetic network

Adenylate kinase phosphotransfer communicates cellular energetic signals to ATP-sensitive potassium channels.

Item does not contain fulltextTransduction of energetic signals into membrane electrical events governs vital cellular functions, ranging from hormone secretion and cytoprotection to appetite control and hair growth. Central to the regulation of such diverse cellular processes are the metabolism sensing ATP-sensitive K+ (K(ATP)) channels. However, the mechanism that communicates metabolic signals and integrates cellular energetics with K(ATP) channel-dependent membrane excitability remains elusive. Here, we identify that the response of K(ATP) channels to metabolic challenge is regulated by adenylate kinase phosphotransfer. Adenylate kinase associates with the K(ATP) channel complex, anchoring cellular phosphotransfer networks and facilitating delivery of mitochondrial signals to the membrane environment. Deletion of the adenylate kinase gene compromised nucleotide exchange at the channel site and impeded communication between mitochondria and K(ATP) channels, rendering cellular metabolic sensing defective. Assigning a signal processing role to adenylate kinase identifies a phosphorelay mechanism essential for efficient coupling of cellular energetics with K(ATP) channels and associated functions

ADH5-mediated NO bioactivity maintains metabolic homeostasis in brown adipose tissue.

Brown adipose tissue (BAT) thermogenic activity is tightly regulated by cellular redox status, but the underlying molecular mechanisms are incompletely understood. Protein S-nitrosylation, the nitric-oxide-mediated cysteine thiol protein modification, plays important roles in cellular redox regulation. Here we show that diet-induced obesity (DIO) and acute cold exposure elevate BAT protein S-nitrosylation, including UCP1. This thermogenic-induced nitric oxide bioactivity is regulated by S-nitrosoglutathione reductase (GSNOR; alcohol dehydrogenase 5 [ADH5]), a denitrosylase that balances the intracellular nitroso-redox status. Loss of ADH5 in BAT impairs cold-induced UCP1-dependent thermogenesis and worsens obesity-associated metabolic dysfunction. Mechanistically, we demonstrate that Adh5 expression is induced by the transcription factor heat shock factor 1 (HSF1), and administration of an HSF1 activator to BAT of DIO mice increases Adh5 expression and significantly improves UCP1-mediated respiration. Together, these data indicate that ADH5 controls BAT nitroso-redox homeostasis to regulate adipose thermogenesis, which may be therapeutically targeted to improve metabolic health