Phosphotyrosine-containing lactate dehydrogenase is restricted to the nuclei of PC12 pheochromocytoma cells.
There are five lactate dehydrogenase (LDH) isoenzymes, composed of various combinations of two types of subunits. LDH-5, which contains only the LDH A subunit, is known to be present in both the cytoplasm and the nucleus, to act as a single-stranded DNA-binding protein possibly functioning in transcription and/or replication, and to undergo phosphorylation of tyrosine 238 in approximately 1% of the enzyme after cell transformation by certain tumor viruses. We have characterized LDH from wild-type PC12 pheochromocytoma cells and from a PC12 variant (MPT1) that exhibits altered lactate metabolism and altered expression of multiple genes. Wild-type and MPT1 cells contain different proportions of LDH isoenzymes, with LDH-5 being more predominant in wild-type cells than in the variant. A small fraction of LDH from PC12 cells contains phosphotyrosine. Approximately 99% of the total LDH activity is located in the cytoplasm, but all of the phosphotyrosine-containing LDH is located in the nucleus. Furthermore, essentially all of the nuclear LDH contains phosphotyrosine. These results suggest that tyrosine phosphorylation can affect its role in the nucleus.
Department of Biological Chemistry, School of Medicine, University of California, Los Angeles 90024.
X H
XH
Zhong
B D
BD
Howard
D000310:Adrenal Gland Neoplasms / Q000201:enzymology; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology*; D002846:Chromatography, Affinity; D003593:Cytoplasm / Q000201:enzymology; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000302:isolation & purification* / Q000378:metabolism; D010673:Pheochromocytoma / Q000201:enzymology; D010710:Phosphates / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D019000:Phosphotyrosine; D051381:Rats; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis; D014638:Vanadates / Q000494:pharmacology
D004268:DNA-Binding Proteins; D007527:Isoenzymes; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D019000:Phosphotyrosine; D014638:Vanadates; D014443:Tyrosine; D007770:L-Lactate Dehydrogenase