Characterisation of phospholipase C-η enzymes and their relevance to disease

Phospholipase C;Enzyme activation;Neurons--Differentiation;Intracellular calcium;Cellular signal transduction

Arastoo, Mohammed ; Stewart, Alan J. ; Stewart, Alan J.

University:University of St Andrews

Department:Medicine (School of)

关键词: Phospholipase C;    Enzyme activation;    Neurons--Differentiation;    Intracellular calcium;    Cellular signal transduction;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/15698/MohammedArastooPhDThesis.pdf?sequence=2&isAllowed=y

来源: DR-NTU

【 摘 要 】

Phospholipase C enzymes are a class of enzymes that catalyse the cleavage of the membranephospholipid, phosphatidylinositol bisphosphate (PtdIns(4,5)P₂) into the second messengers,inositol trisphosphate (Ins(4,5)P₃) and diacylglycerol (DAG). Six classes of PLC enzymes havebeen identified based on their structure and mechanism of activation.PLCηs are the most recently identified family and consist of two isozymes, PLCη1 and PLCη2.The aim of this thesis is to further understand the mechanisms of PLCη activation, the role ofPLCη2 in relation to neuritogenesis and their roles in certain disease states. Both isoforms werefound to be activated by physiological concentrations of intracellular Ca²⁺. Activation ofPLCη2 by Gß₁γ₂ was confirmed using a bacterial 2A co-expression system to allow expressionof PLCη2, Gß₁ and Gγ₂ with a single plasmid. Localisation studies show a nuclear distributionfor PLCη2, but a cytoplasmic distribution for PLCη1 in a neuroblastoma cells line (Neuro2A).PLCη2 has been implicated in brain development and neurite formation. Building on this, aneuronal differentiation model using RA-treated Neuro2A cells stably expressing mutant formsof PLCη2 was utilised, revealing that PLCη2 activity is essential for neuritogenesis but thatthis process is independent of the enzymes high sensitivity towards Ca²⁺. Furthermore, the direct interaction of PLCη2 and LIMK-1, a previously identified PLCη2 associated protein, is confirmed in the aforementioned neuronal model. Due to the high sensitivity of PLCη enzymes to Ca²⁺ and because of their presence within neurons, they may be involved in Ca²⁺ dysregulation that occurs in certain diseases such as Alzheimer’s disease (AD). The role of PLCη2 was assessed in amyloid-ß (Aß) treateddifferentiated Neuro2A cells, a cellular model for AD pathogenesis. Also a developmental role for PLCη1 was investigated due to a recently identified PLCη1 polymorphism in patients with holoprosencephaly, an embryonic midline defect.