Hypoxia and AMP independently regulate AMP-activated protein kinase activity in heart. Export

@article{citeulike:379678, abstract = {The hypothesis was tested that hypoxia increases AMP-activated protein kinase (AMPK) activity independently of AMP concentration ([AMP]) in heart. In isolated perfused rat hearts, cytosolic [AMP] was changed from 0.2 to 16 microM using metabolic inhibitors during both normal oxygenation (95\% O2-5\% CO2, normoxia) and limited oxygenation (95\% N2-5\% CO2, hypoxia). Total AMPK activity measured in vitro ranged from 2 to 40 pmol.min(-1).mg protein(-1) in normoxic hearts and from 5 to 55 pmol.min(-1).mg protein(-1) in hypoxic hearts. The dependence of the in vitro total AMPK activity on the in vivo cytosolic [AMP] was determined by fitting the measurements from individual hearts to a hyperbolic equation. The [AMP] resulting in half-maximal total AMPK activity (A0.5) was 3 +/- 1 microM for hypoxic hearts and 28 +/- 13 microM for normoxic hearts. The A0.5 for alpha2-isoform AMPK activity was 2 +/- 1 microM for hypoxic hearts and 13 +/- 8 microM for normoxic hearts. Total AMPK activity correlated with the phosphorylation of the Thr172 residue of the AMPK alpha-subunit. In potassium-arrested hearts perfused with variable O2 content, alpha-subunit Thr172 phosphorylation increased at O2 < or = 21\% even though [AMP] was <0.3 microM. Thus hypoxia or O2 < or = 21\% increased AMPK phosphorylation and activity independently of cytosolic [AMP]. The hypoxic increase in AMPK activity may result from either direct phosphorylation of Thr172 by an upstream kinase or reduction in the A0.5 for [AMP].}, address = {Nuclear Magnetic Resonance Laboratory for Physiological Chemistry, Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.}, author = {Frederich, M. and Zhang, L. and Balschi, J. A.}, citeulike-article-id = {379678}, citeulike-linkout-0 = {http://dx.doi.org/10.1152/ajpheart.00558.2004}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/15637122}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=15637122}, doi = {10.1152/ajpheart.00558.2004}, issn = {0363-6135}, journal = {Am J Physiol Heart Circ Physiol}, keywords = {amp, heart, hypoxia, ischemia, kinase, myocardium}, month = {May}, number = {5}, posted-at = {2005-11-03 18:08:54}, priority = {3}, title = {Hypoxia and AMP independently regulate AMP-activated protein kinase activity in heart.}, url = {http://dx.doi.org/10.1152/ajpheart.00558.2004}, volume = {288}, year = {2005} }

TY - JOUR ID - citeulike:379678 L3 - citeulike-article-id:379678 N2 - The hypothesis was tested that hypoxia increases AMP-activated protein kinase (AMPK) activity independently of AMP concentration ([AMP]) in heart. In isolated perfused rat hearts, cytosolic [AMP] was changed from 0.2 to 16 microM using metabolic inhibitors during both normal oxygenation (95% O2-5% CO2, normoxia) and limited oxygenation (95% N2-5% CO2, hypoxia). Total AMPK activity measured in vitro ranged from 2 to 40 pmol.min(-1).mg protein(-1) in normoxic hearts and from 5 to 55 pmol.min(-1).mg protein(-1) in hypoxic hearts. The dependence of the in vitro total AMPK activity on the in vivo cytosolic [AMP] was determined by fitting the measurements from individual hearts to a hyperbolic equation. The [AMP] resulting in half-maximal total AMPK activity (A0.5) was 3 +/- 1 microM for hypoxic hearts and 28 +/- 13 microM for normoxic hearts. The A0.5 for alpha2-isoform AMPK activity was 2 +/- 1 microM for hypoxic hearts and 13 +/- 8 microM for normoxic hearts. Total AMPK activity correlated with the phosphorylation of the Thr172 residue of the AMPK alpha-subunit. In potassium-arrested hearts perfused with variable O2 content, alpha-subunit Thr172 phosphorylation increased at O2 < or = 21% even though [AMP] was <0.3 microM. Thus hypoxia or O2 < or = 21% increased AMPK phosphorylation and activity independently of cytosolic [AMP]. The hypoxic increase in AMPK activity may result from either direct phosphorylation of Thr172 by an upstream kinase or reduction in the A0.5 for [AMP]. IS - 5 JF - Am J Physiol Heart Circ Physiol SN - 0363-6135 AD - Nuclear Magnetic Resonance Laboratory for Physiological Chemistry, Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA. TI - Hypoxia and AMP independently regulate AMP-activated protein kinase activity in heart. VL - 288 KW - amp KW - heart KW - hypoxia KW - ischemia KW - kinase KW - myocardium AU - Frederich, M AU - Zhang, L AU - Balschi, JA PY - 2005/05// UR - http://dx.doi.org/10.1152/ajpheart.00558.2004 ER -