title: M-LDH serves as a regulatory subunit of the cytosolic substrate-channelling complex in vivo.
abstract: Nucleoside diphosphate kinase A (NDPK-A) regulates the alpha1 isoform of the AMP-activated protein kinase (AMPK alpha1) selectively, independent of [AMP] and surrounding [ATP], by a process termed substrate channelling. Here, we show, using a range of empirically validated biochemical techniques, that the muscle form (M-LDH or LDH-A) and the heart form (H-LDH or LDH-B) of lactate dehydrogenase are physically associated with the liver cytosolic substrate-channelling complex such that M-LDH associates with NDPK-A, AMPK alpha1 and casein kinase 2 (CK2), whereas H-LDH associates with local NDPK-B. We find that the species of LDH bound to the substrate-channelling complex regulates the in vivo enzymatic activities of both AMPK and CK2, and has a downstream effect on the phospho-status of acetyl CoA carboxylase, a key regulator of cellular fat metabolism known to be a part of the cytosolic substrate-channelling complex in vivo. We hypothesise that the regulatory presence of LDH in the complex couples the substrate-channelling mechanism to both the glycolytic and redox states of the cell, allowing for efficient sensing of cell metabolic status, interfacing with the substrate-channelling complex and regulating the enzymatic activities of AMPK and CK2, two critical protein kinases.
authors.affiliation: Maternal and Child Health Sciences, University of Dundee, Ninewells Hospital, Dundee, DD1 9SY, UK.
authors.forename: Sofija
authors.initials: S
authors.lastname: Jovanović
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Jovanović
authors.forename: Russell M
authors.initials: RM
authors.lastname: Crawford
mesh_terms: D000818:Animals; D003600:Cytosol / Q000201:enzymology*; D007525:Isoelectric Focusing; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009206:Myocardium / Q000201:enzymology*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D020033:Protein Isoforms; D021122:Protein Subunits; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D007770:L-Lactate Dehydrogenase