Mechanisms involved in XXXX -mobilizing agonist responses.

@entity2366 @entity8580 @entity19077 @entity1425 @entity2178 @entity1951 @entity377 @entity2774 @entity8586 @entity1919 @entity460 @entity141 @entity669 @entity1063 @entity11396 @entity4357 @entity934
Many hormones and neurotransmitters exert their biological effects by increasing the levels of @entity141 and @entity11396 in their target cells. Major agonists that act in this way are @entity1425 and @entity1063 , @entity934 , @entity1951 , @entity8586 , and @entity2178 . These and other @entity141 -mobilizing agonists may also produce effects that are not mediated by @entity141 or @entity2366 , but involve separate receptors and an increase or decrease in @entity1919 . The general mechanisms by which @entity141 -mobilizing agonists induce their physiological responses are depicted in Fig. 12. These responses appear to involve an initial mobilization of @entity141 from endoplasmic reticulum and perhaps other intracellular @entity141 stores, followed by alterations in the flux of @entity141 across the plasma membrane. The @entity141 changes are consistently associated with increased turnover of cellular phosphoinositides. The most rapid response is breakdown of @entity4357 4,5-P2 in the plasma membrane, and there is much evidence that this involves a @entity2774 - @entity377 -binding regulatory protein similar to those involved in the regulation of adenylate cyclase. Myo- @entity8580 1,4,5-P3 produced by @entity4357 4,5-P2 breakdown rapidly releases @entity141 from endoplasmic reticulum, and it is likely that it is the long-sought second message for the @entity141 -dependent hormones. @entity11396 , the other product of @entity4357 4,5-P2 breakdown, also acts as a second message in that it activates protein kinase C, a @entity141 -phospholipid-dependent protein kinase, by lowering its requirement for @entity141 . The cellular substrates for protein kinase C and its role in the different physiological responses to the @entity141 -mediated agonists are currently being defined. The major intracellular target for @entity141 is the @entity141 -dependent regulatory protein calmodulin. This binds @entity141 with high affinity, and the resulting complex interacts with a variety of enzymes and other cellular proteins, modifying their activities. A major target is the multifunctional calmodulin-dependent protein kinase that phosphorylates and alters the activities of many proteins, for example, glycogen synthase and @entity669 hydroxylase. @entity460 ions may also stimulate calmodulin-dependent protein kinases that are more specific, such as phosphorylase kinase and @entity19077 . Other important @entity141 -calmodulin targets are the microtubule-associated proteins, but it is likely that many more will be found.(ABSTRACT TRUNCATED AT 400 WORDS)
