Methods for the Analysis of Phosphoinositides and Inositol Phosphates

互联网2014-02-14

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There is now compelling evidence that stimulation of inosito1 phospholipid metabolism via phosphoinositidase C (MC) is the signal transduction pathway for a wide variety of receptors in the mammalian nervous system. A by no means comprehensive list is shown in Table 1 . Receptors are thought to be coupled to PIC through a guanine nucleotide-binding protein (G protein—see Chapter 1 by Milligan) termed G , by a mechanism analogous to coupling of receptors with adenylyl cyclase, though as yet the identity of this G protein has not been established.* (For general reviews, see Hawthorne and Pickard, 1979 ; Downes, 1986 ; Fisher and Agranoff, 1987 ; Watson and Godfrey, 1988 ; Berridge and Irvine, 1989 ; Nahorski and Potter, 1989 ). The initial receptor-coupled event is a PIC-mediated breakdown of phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P₂ ) to give the two intracellular messengers inositol 1,4,5-trisphosphate (Ins(1,4,5)P)₃ which mobilizes intracellular Ca²⁺ (see Chapter 3 by Taylor et al.), and 1,2-diacylglycerol (DG), which activates protein kinase C (see Chapter 6 by Burgess). Ins (1,4,5)P₃ is then either phosphorylated to inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P₄ ) or dephosphorylated to Ins(1,4)P_3′ , the reactions catalyzed by a 3kinase or 5-phosphatase, respectively.

Table 1 Receptors Known To Be Coupled to PIC in the CNS or Related Cell Lines

Receptor	Subtype(s)	Tissue
Muscarinic	ml, m3, m5	Brain slices
		Neuronal cell lines
		Neuronal and glial primary cultures
		Transfected cell lines
Adrenergic	α₁	Brain slices
		Synaptoneurosomes
		Primary cultures
		Transfected cell lines
Histaminergic	H₁	Brain slices
		Neuronal cell lines
Serotonergic	5-HT_1C' 5-HT₂	Brain slices
		Choroid plexus
		Neuronal cell lines
		Transfected cell lines
Glutamatergic	Quis/metabotropic	Brain slices
		Cerebellar granule cells
		Primary neuronal culture
Tachykinin	NK1, NK2, NK3	Brain slices
		Astrocytoma cell lines
Neurotensin		Brain slices
		Neuronal cell lines
Bradykinin		Neuronal cell lines
CCK		Brain slices
Vasopressin		Brain slices
		SCG^a
Depolarization		Brain slice
		SCG^a

^a SCG—superior cervical ganglion.