TY - JOUR
T1 - Identification of Li+ binding sites and the effect of Li + treatment on phospholipid composition in human neuroblastoma cells
T2 - A 7Li and 31P NMR study
AU - Layden, Brian T.
AU - Abukhdeir, Abde M.
AU - Malarkey, Christopher
AU - Oriti, Lisa A.
AU - Salah, Wajeeh
AU - Stigler, Claire
AU - Geraldes, Carlos F G C
AU - De Freitas, Duarte Mota
N1 - Funding Information:
D. M. F. is grateful for financial support from the National Institute of Mental Health (MH-45926) and DARPA (N66001-03-1-8941), and the National Science Foundation (DBI-0216630) for the acquisition of the Varian INOVA-300 NMR spectrometer. L. A. O. was supported by an NSF-REU Training Grant (CHE-0243825) and C. M. by a GAANN Fellowship from the US Department of Education (P200A00200-00). C. F. G. C. G. acknowledges support from FCT, Portugal (grant POCTI/1999/36160) and FEDER.
PY - 2005/9/25
Y1 - 2005/9/25
N2 - Li+ binding in subcellular fractions of human neuroblastoma SH-SY5Y cells was investigated using 7Li NMR spin-lattice (T 1) and spin-spin (T2) relaxation measurements, as the T1/T2 ratio is a sensitive parameter of Li+ binding. The majority of Li+ binding occurred in the plasma membrane, microsomes, and nuclear membrane fractions as demonstrated by the Li + binding constants and the values of the T1/T2 ratios, which were drastically larger than those observed in the cytosol, nuclei, and mitochondria. We also investigated by 31P NMR spectroscopy the effects of chronic Li+ treatment for 4-6 weeks on the phospholipid composition of the plasma membrane and the cell homogenate and found that the levels of phosphatidylinositol and phosphatidylserine were significantly increased and decreased, respectively, in both fractions. From these observations, we propose that Li+ binding occurs predominantly to membrane domains, and that chronic Li+ treatment alters the phospholipid composition at these membrane sites. These findings support those from clinical studies that have indicated that Li+ treatment of bipolar patients results in irregularities in Li+ binding and phospholipid metabolism. Implications of our observations on putative mechanisms of Li+ action, including the cell membrane abnormality, the inositol depletion and the G-protein hypotheses, are discussed.
AB - Li+ binding in subcellular fractions of human neuroblastoma SH-SY5Y cells was investigated using 7Li NMR spin-lattice (T 1) and spin-spin (T2) relaxation measurements, as the T1/T2 ratio is a sensitive parameter of Li+ binding. The majority of Li+ binding occurred in the plasma membrane, microsomes, and nuclear membrane fractions as demonstrated by the Li + binding constants and the values of the T1/T2 ratios, which were drastically larger than those observed in the cytosol, nuclei, and mitochondria. We also investigated by 31P NMR spectroscopy the effects of chronic Li+ treatment for 4-6 weeks on the phospholipid composition of the plasma membrane and the cell homogenate and found that the levels of phosphatidylinositol and phosphatidylserine were significantly increased and decreased, respectively, in both fractions. From these observations, we propose that Li+ binding occurs predominantly to membrane domains, and that chronic Li+ treatment alters the phospholipid composition at these membrane sites. These findings support those from clinical studies that have indicated that Li+ treatment of bipolar patients results in irregularities in Li+ binding and phospholipid metabolism. Implications of our observations on putative mechanisms of Li+ action, including the cell membrane abnormality, the inositol depletion and the G-protein hypotheses, are discussed.
KW - Cell membrane
KW - Cytosol
KW - Lithium
KW - Mitochondria
KW - NMR
KW - Phospholipid
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U2 - 10.1016/j.bbadis.2005.07.004
DO - 10.1016/j.bbadis.2005.07.004
M3 - Article
C2 - 16115751
AN - SCOPUS:25144523535
SN - 0925-4439
VL - 1741
SP - 339
EP - 349
JO - Biochimica et Biophysica Acta - Molecular Basis of Disease
JF - Biochimica et Biophysica Acta - Molecular Basis of Disease
IS - 3
ER -