PMID- 33337958 OWN - NLM STAT- MEDLINE DCOM- 20210322 LR - 20240226 IS - 1522-1539 (Electronic) IS - 0363-6135 (Linking) VI - 320 IP - 2 DP - 2021 Feb 1 TI - Cardiac expression and location of hexokinase changes in a mouse model of pure creatine deficiency. PG - H613-H629 LID - 10.1152/ajpheart.00188.2020 [doi] AB - Creatine kinase (CK) is considered the main phosphotransfer system in the heart, important for overcoming diffusion restrictions and regulating mitochondrial respiration. It is substrate limited in creatine-deficient mice lacking l-arginine:glycine amidinotransferase (AGAT) or guanidinoacetate N-methyltranferase (GAMT). Our aim was to determine the expression, activity, and mitochondrial coupling of hexokinase (HK) and adenylate kinase (AK), as these represent alternative energy transfer systems. In permeabilized cardiomyocytes, we assessed how much endogenous ADP generated by HK, AK, or CK stimulated mitochondrial respiration and how much was channeled to mitochondria. In whole heart homogenates, and cytosolic and mitochondrial fractions, we measured the activities of AK, CK, and HK. Lastly, we assessed the expression of the major HK, AK, and CK isoforms. Overall, respiration stimulated by HK, AK, and CK was approximately 25, 90, and 80%, respectively, of the maximal respiration rate, and approximately 20, 0, and 25%, respectively, was channeled to the mitochondria. The activity, distribution, and expression of HK, AK, and CK did not change in GAMT knockout (KO) mice. In AGAT KO mice, we found no changes in AK, but we found a higher HK activity in the mitochondrial fraction, greater expression of HK I, but a lower stimulation of respiration by HK. Our findings suggest that mouse hearts depend less on phosphotransfer systems to facilitate ADP flux across the mitochondrial membrane. In AGAT KO mice, which are a model of pure creatine deficiency, the changes in HK may reflect changes in metabolism as well as influence mitochondrial regulation and reactive oxygen species production.NEW & NOTEWORTHY In creatine-deficient AGAT(-/-) and GAMT(-/-) mice, the myocardial creatine kinase system is substrate limited. It is unknown whether subcellular localization and mitochondrial ADP channeling by hexokinase and adenylate kinase may compensate as alternative phosphotransfer systems. Our results show no changes in adenylate kinase, which is the main alternative to creatine kinase in heart. However, we found increased expression and activity of hexokinase I in AGAT(-/-) cardiomyocytes. This could affect mitochondrial regulation and reactive oxygen species production. FAU - Branovets, Jelena AU - Branovets J AUID- ORCID: 0000-0001-7970-8543 AD - Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia. FAU - Karro, Niina AU - Karro N AUID- ORCID: 0000-0002-3231-0789 AD - Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia. FAU - Barsunova, Karina AU - Barsunova K AD - Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia. FAU - Laasmaa, Martin AU - Laasmaa M AUID- ORCID: 0000-0002-6663-6947 AD - Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia. FAU - Lygate, Craig A AU - Lygate CA AD - Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom. FAU - Vendelin, Marko AU - Vendelin M AUID- ORCID: 0000-0002-6459-0391 AD - Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia. FAU - Birkedal, Rikke AU - Birkedal R AUID- ORCID: 0000-0001-6777-7031 AD - Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia. LA - eng GR - RG/18/12/34040/BHF_/British Heart Foundation/United Kingdom GR - RG/18/12/34040/British Heart Foundation (BHF)/ PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20201218 PL - United States TA - Am J Physiol Heart Circ Physiol JT - American journal of physiology. Heart and circulatory physiology JID - 100901228 RN - 61D2G4IYVH (Adenosine Diphosphate) RN - EC 2.1.1.2 (Gamt protein, mouse) RN - EC 2.1.1.2 (Guanidinoacetate N-Methyltransferase) RN - EC 2.1.4.- (Amidinotransferases) RN - EC 2.1.4.1 (glycine amidinotransferase) RN - EC 2.7.1.1 (Hexokinase) RN - EC 2.7.3.2 (Creatine Kinase) RN - EC 2.7.4.3 (Adenylate Kinase) RN - MU72812GK0 (Creatine) RN - Arginine-Glycine Amidinotransferase Deficiency RN - Guanidinoacetate methyltransferase deficiency SB - IM MH - Adenosine Diphosphate/metabolism MH - Adenylate Kinase/metabolism MH - Amidinotransferases/*deficiency/genetics MH - Amino Acid Metabolism, Inborn Errors/*enzymology/genetics MH - Animals MH - Cell Respiration MH - Creatine/*deficiency MH - Creatine Kinase/metabolism MH - Developmental Disabilities/enzymology/genetics MH - Disease Models, Animal MH - *Energy Metabolism MH - Female MH - Guanidinoacetate N-Methyltransferase/*deficiency/genetics MH - Hexokinase/*metabolism MH - Intellectual Disability/*enzymology/genetics MH - Language Development Disorders/*enzymology/genetics MH - Male MH - Mice, Inbred C57BL MH - Mice, Knockout MH - Mitochondria, Heart/*enzymology MH - Movement Disorders/*congenital/enzymology/genetics MH - Myocytes, Cardiac/*enzymology MH - Speech Disorders/*enzymology/genetics MH - Mice OTO - NOTNLM OT - adenylate kinase OT - cardiac energetics OT - creatine kinase OT - creatine-deficient mice OT - hexokinase EDAT- 2020/12/19 06:00 MHDA- 2021/03/23 06:00 CRDT- 2020/12/18 17:09 PHST- 2020/12/19 06:00 [pubmed] PHST- 2021/03/23 06:00 [medline] PHST- 2020/12/18 17:09 [entrez] AID - 10.1152/ajpheart.00188.2020 [doi] PST - ppublish SO - Am J Physiol Heart Circ Physiol. 2021 Feb 1;320(2):H613-H629. doi: 10.1152/ajpheart.00188.2020. Epub 2020 Dec 18.