The main component of brain amyloid plaques, present in Alzheimer's disease, is AbetaP, a proteolytic product of the amyloid precursor protein (APP). Previous reports have indicated that cell death can be caused by alteration of calcium homeostasis to channel formation of the AbetaP peptide. We found that AbetaP shows a high affinity for Ox Ch BLM in which it forms channels with biophysical characteristics that are different from those formed in phospholipid BLM (Micelli S. et al., 2003 EBSA). This result is of interest because cholesterol and its oxidation products are abundant in the membrane lipid domains of brain cells (Galbete J.L. et al., 2000. Biochem.J. 348:307-313). Furthermore, recent studies have shown that AbetaP peptide significantly reduces the activity of enzymes such as Cl--ATPase and Na+-K+-ATPase in AD brain (Hattori N. et al., 1998. Neurosciences Letters, vol.254: 141-144). The aim of this study was to examine whwther Na+-K+-ATPase activity was directly affected by AbetaP(1-40). For this purpose, enzyme-enriched membranes from the hemisphere of horse brain were prepared as described by Jorgensen (1988 Methods Enzymology, 156: 29-43). Na+-K+-ATPase activity was determined by spectrophotometric measurement of the inorganic phosphate liberated.The incubation times for AbetaP (0.5uM) with Na+-K+-ATPase crude membranes were 30 and 60 min. Our results indicate that Na+-K+-APTase activity was not inhibited at 30 min, though it was slightly inhibited (18%) at 60 min. Besides, AbetaP seems to inhibit the phosphorylated form much more than the dephosphorylated one. These results suggest that the main factor responsible for AD could be the ionic imbalance determined by AbetaP through both channel formation and direct inhibition of Na+-K+-ATPase activity.
Effect of AbP(1-40) on Na+,K+-ATPase activity in crude horse brain membranes
MELELEO D.;C. DE LUCA;
2003-01-01
Abstract
The main component of brain amyloid plaques, present in Alzheimer's disease, is AbetaP, a proteolytic product of the amyloid precursor protein (APP). Previous reports have indicated that cell death can be caused by alteration of calcium homeostasis to channel formation of the AbetaP peptide. We found that AbetaP shows a high affinity for Ox Ch BLM in which it forms channels with biophysical characteristics that are different from those formed in phospholipid BLM (Micelli S. et al., 2003 EBSA). This result is of interest because cholesterol and its oxidation products are abundant in the membrane lipid domains of brain cells (Galbete J.L. et al., 2000. Biochem.J. 348:307-313). Furthermore, recent studies have shown that AbetaP peptide significantly reduces the activity of enzymes such as Cl--ATPase and Na+-K+-ATPase in AD brain (Hattori N. et al., 1998. Neurosciences Letters, vol.254: 141-144). The aim of this study was to examine whwther Na+-K+-ATPase activity was directly affected by AbetaP(1-40). For this purpose, enzyme-enriched membranes from the hemisphere of horse brain were prepared as described by Jorgensen (1988 Methods Enzymology, 156: 29-43). Na+-K+-ATPase activity was determined by spectrophotometric measurement of the inorganic phosphate liberated.The incubation times for AbetaP (0.5uM) with Na+-K+-ATPase crude membranes were 30 and 60 min. Our results indicate that Na+-K+-APTase activity was not inhibited at 30 min, though it was slightly inhibited (18%) at 60 min. Besides, AbetaP seems to inhibit the phosphorylated form much more than the dephosphorylated one. These results suggest that the main factor responsible for AD could be the ionic imbalance determined by AbetaP through both channel formation and direct inhibition of Na+-K+-ATPase activity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
