A variety of extracellular signals are transduced across the cell membrane by the enzyme phosphoinositide-specific phospholipase C-beta (PLC-beta) coupled with guanine-nucleotide-binding G proteins. There are four isoenzymes of PLC-beta, beta1-beta4, but their functions in vivo are not known. Here we investigate the role of PLC-beta1 and PLC-beta4 in the brain by generating null mutations in mice: we found that PLCbeta1-/- mice developed epilepsy and PLCbeta4-/- mice showed ataxia. We determined the molecular basis of these phenotypes and show that PLC-beta1 is involved in signal transduction in the cerebral cortex and hippocampus by coupling predominantly to the muscarinic acetylcholine receptor, whereas PLC-beta4 works through the metabotropic glutamate receptor in the cerebellum, illustrating how PLC-beta isoenzymes are used to generate different functions in the brain.

Human DJ-1 and Escherichia coli Hsp31 belong to ThiJ/PfpI family, whose members contain a conserved domain. DJ-1 is associated with autosomal recessive early onset parkinsonism and Hsp31 is a molecular chaperone. Structural comparisons between DJ-1, Hsp31, and an Archaea protease, a member of ThiJ/PfpI family, lead to the identification of the chaperone activity of DJ-1 and the proteolytic activity of Hsp31. Moreover, the comparisons provide insights into how the functional diversity is realized in proteins that share an evolutionarily conserved domain. On the basis of the chaperone activity the possible role of DJ-1 in the pathogenesis of Parkinson's disease is discussed.

We report here that PLC-gamma isoforms are required for agonist-induced Ca2+ entry (ACE). Overexpressed wild-type PLC-gamma1 or a lipase-inactive mutant PLC-gamma1 each augmented ACE in PC12 cells, while a deletion mutant lacking the region containing the SH3 domain of PLC-gamma1 was ineffective. RNA interference to deplete either PLC-gamma1 or PLC-gamma2 in PC12 and A7r5 cells inhibited ACE. In DT40 B lymphocytes expressing only PLC-gamma2, overexpressed muscarinic M5 receptors (M5R) activated ACE. Using DT40 PLC-gamma2 knockout cells, M5R stimulation of ER Ca2+ store release was unaffected, but ACE was abolished. Normal ACE was restored by transient expression of PLC-gamma2 or a lipase-inactive PLC-gamma2 mutant. The results indicate a lipase-independent role of PLC-gamma in the physiological agonist-induced activation of Ca2+ entry.

BackgroundThe Notch signaling pathway is an evolutionarily conserved intercellular signaling module essential for cell fate specification that requires endocytosis of Notch ligands. Structurally distinct E3 ubiquitin ligases, Neuralized (Neur) and Mind bomb (Mib), cooperatively regulate the endocytosis of Notch ligands in Drosophila. However, the respective roles of the mammalian E3 ubiquitin ligases, Neur1, Neur2, Mib1, and Mib2, in mammalian development are poorly understood.Methodology/Principal FindingsThrough extensive use of mammalian genetics, here we show that Neur1 and Neur2 double mutants and Mib2−/− mice were viable and grossly normal. In contrast, conditional inactivation of Mib1 in various tissues revealed the representative Notch phenotypes: defects of arterial specification as deltalike4 mutants, abnormal cerebellum and skin development as jagged1 conditional mutants, and syndactylism as jagged2 mutants.Conclusions/SignificanceOur data provide the first evidence that Mib1 is essential for Jagged as well as Deltalike ligand-mediated Notch signaling in mammalian development, while Neur1, Neur2, and Mib2 are dispensable.

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