Acetylcholine content and viability of cholinergic neurons are influenced by the activity of protein histidine phosphatase

Abstract

BackgroundThe first mammalian protein histidine phosphatase (PHP) was discovered in the late 90s of the last century. One of the known substrates of PHP is ATP-citrate lyase (ACL), which is responsible - amongst other functions - for providing acetyl-CoA for acetylcholine synthesis in neuronal tissues. It has been shown in previous studies that PHP downregulates the activity of ACL by dephosphorylation. According to this our present work focused on the influence of PHP activity on the acetylcholine level in cholinergic neurons.ResultsThe amount of PHP in SN56 cholinergic neuroblastoma cells was increased after overexpression of PHP by using pIRES2-AcGFP1-PHP as a vector. We demonstrated that PHP overexpression reduced the acetylcholine level and induced cell death. The acetylcholine content of SN56 cells was measured by fast liquid chromatography-tandem mass spectrometry method. Overexpression of the inactive H53A-PHP mutant also induced cell damage, but in a significantly reduced manner. However, this overexpression of the inactive PHP mutant did not change the acetylcholine content of SN56 cells significantly. In contrast, PHP downregulation, performed by RNAi-technique, did not induce cell death, but significantly increased the acetylcholine content in SN56 cells.ConclusionsWe could show for the first time that PHP downregulation increased the acetylcholine level in SN56 cells. This might be a potential therapeutic strategy for diseases involving cholinergic deficits like Alzheimer's disease.

Metabolic and Cellular Compartments of Acetyl-CoA in the Healthy and Diseased Brain

“…In SN56 cholinergic neurons, dephosphorylation of ACLY by overexpression of protein histidine phosphatase (PHP) inhibited enzyme activity, resulting in a 30% reduction in ACh content and 10% loss of cell viability. Suppression of PHP by specific siRNA restored ACh content and cell viability [ 141 , 142 ]. These data indicate that the fractional contribution of the ACLY pathway to the cytoplasmic acetyl-CoA pool for ACh synthesis in cholinergic neurons is lower than that for fatty acid synthesis in oligodendrocytes [ 133 , 136 , 143 ].…”