ISSN:
1573-4919
Keywords:
phosphoinositides
;
phosphatidylcholine
;
phospholipases
;
diacylglycerol
;
phosphatidate
;
calcium
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract There is much evidence that G-proteins transduce the signal from receptors for Ca2+-mobilizing agonists to the phospholipase C that catalyzes the hydrolysis of phosphoinositides. However, the specific G-proteins involved have not been identified. We have recently purified a 42 kDa protein from liver that activates phosphoinositide phospholipase C and cross-reacts with antisera to a peptide common to G-protein α-subunits. It is proposed that this protein is the a-subunit of the G-protein that regulates the phospholipase in this tissue. Ca2+-mobilizing agonists and certain growth factors also promote the hydrolysis of phosphatidylcholine through the activation of phospholipases C and D in many cell types. This yields a larger amount of diacylglycerol for a longer time than does the hydrolysis of inositol phospholipids. Consequently phosphatidylcholine breakdown is probably a major factor in long-term regulation of protein kinase C. The functions of phosphatidic acid produced by phospholipase D are speculative, but there is evidence that it is a major source of diacylglycerol in many cell types. The regulation of phosphatidylcholine phospholipases is multiple and involves direct activation by G-proteins, and regulation by Ca2+ protein kinase C and perhaps growth factor receptor tyrosine kinases.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00229807
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