High-affinity Ca(2+) transport ATPases play a crucial role in controlling cytosolic Ca(2+). The amyloid beta-peptide (Abeta) is a neurotoxic agent found in affected neurons in Alzheimer's disease (AD) that has been implicated in dysregulation of Ca(2+) homeostasis. Using kinetic assays, we have shown that the Ca(2+) dependencies of intracellular Ca(2+)-ATPase (SERCA and SPCA) activity are the same in human AD and normal brain but that of plasma membrane Ca(2+)-ATPase (PMCA) is different. The addition of Abeta to normal brain decreases the PMCA activity measured at pCa 5.5, resulting in the same Ca(2+)dependency as that seen in AD brain, whereas the addition of Abeta to AD brain has no effect on PMCA activity. Abeta also decreases the activity of PMCA purified from pig cerebrum, the effect being isoform specific. The level of inhibition of purified PMCA caused by Abeta is reduced by cholesterol, and the level of inhibition of PMCA activity by Abeta in the raft fraction of pig synaptosomal membranes is lower than for the nonraft fraction. We conclude that the effect of Abeta on PMCA activity could be important in amyloid toxicity, resulting in cytoplasmic Ca(2+) dysregulation and could explain the different Ca(2+) dependencies of PMCA activity observed in normal and AD brain.

Paediatric cancers often resemble trapped developmental intermediate states that fail to engage the normal differentiation programme, typified by high-risk neuroblastoma arising from the developing sympathetic nervous system. Neuroblastoma cells resemble arrested neuroblasts trapped by a stable but aberant epigenetic programme controlled by sustained expression of a core transcriptional circuit of developmental regulators in conjunction with elevated MYCN or MYC (MYC). The transcription factor ASCL1 is a key master regulator in neuroblastoma and has oncogenic and tumour suppressive activities in several other tumour types. Using functional mutational approaches, we find that preventing CDK-dependent phosphorylation of ASCL1 in neuroblastoma cells drives coordinated suppression of the MYC-driven core circuit supporting neuroblast identity and proliferation, while simultaneously activating an enduring gene programme driving mitotic exit and neuronal differentiation. Implications: These findings indicate that targeting phosphorylation of ASCL1 may offer a new approach to development of differentiation therapies in neuroblastoma.

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Membrane fractions of pig cerebellum show Ca 2+ -ATPase activity and Ca 2+ transport due to the presence of the secretory pathway Ca 2+-ATPase (SPCA). The SPCA1 isoform shows a wide distribution in the neurons of pig cerebellum, where it is found in the Golgi complex of the soma of Purkinje, stellate, basket and granule cells, and also in more distal components of the secretory pathway associated with a synaptic localization such as in cerebellar glomeruli. The SPCA1 may be involved in loading the Golgi complex and the secretory vesicles of these specific neuronal cell types with Ca ) levels as well as the local cytosolic Ca 2+ levels. In addition, it helps to specify the zones that are most vulnerable to Ca 2+ and/or Mn 2+ dyshomeostasis, a condition that is held responsible of an increasing number of neurological disorders.