Protein kinase pathway modulated

Functionally, the Dl-like receptors (Dl, D5) are coupled to the G protein Gas and thus can stimulate adenylyl cyclase. The D2-like receptors (D2, D3, and D4) couple to pertussis toxin sensitive G proteins (Gai/0), and consequently inhibit adenylyl cyclase activity. While the Dl-like receptors almost exclusively signal through Gas-mediated activation of adenylyl cyclase, the D2-like receptors have been reported to modulate the activity of a plethora of signaling molecules and pathways. Many of these actions are mediated through the G(3y subunit. Some of these molecules and pathways include the calcium channels, potassium channels, sodium-hydrogen exchanger, arachidonic acid release, and mitogen-activated protein kinase pathways. 

Xue, J.-F., Liu, Z.-J., Hu, J.-F., Chen, H., Zhang, J.-T., and Chen, N.-H. (2006). Ginsenoside Rbl promotes neurotransmitter release by modulating phosphyrolation of synapsis through a cAMP-dependent protein kinase pathway. Brain Res. 1106, 91-98. 

Yuan LL, Adams JP, Swank M, Sweatt JD, Johnston D. 2002. Protein kinase modulation of dendritic K+ channels in hippocampus involves a mitogen-activated protein kinase pathway. J Neurosci 22 4860-4868. 

Phospholipases of type Cy are activated by receptor tyrosine kinases (see Chapter 8), and thus phospholipase Cy is involved in growth factor-controlled signal transduction pathways. The receptor tyrosine kinases (see Chapter 8) phosphorylate the enzyme at specific tyrosine residues and initiate activation of the enzyme. This activation mobilizes internal calcium stores and engages multiple protein kinase pathways. Characteristic for the structure of phospholipase Cy is the occurrence of SH2 and SH3 domains (see Chapter 8). These represent protein modules that serve to attach upstream and downstream partner proteins. The SH2 domains mediate binding to Tyr-phos-phates of the activated, autophosphorylated receptor tyrosine kinase. During this process, the phospholipase Cy enzymes are phosphorylated onTyr-residues and are thereby activated. 

In addition to PR-mediated transcriptional activities, progesterone also triggers intracellular phosphorylation cascades of the Src/Ras/mitogen-activated protein kinase pathway via PR [10, 11]. Also independent of the transcriptional activities of the receptor are rapid nongenomic effects of progesterone like modulation of sperm acrosome reaction [12], prevention of preterm labor [13] and Xenopus oocyte maturation [14]. 

After a brief overview of signal transduction, the text describes the structure of the seven-helix transmembrane P-adrenergic receptor and indicates how it transmits to the intracellular side of the plasma membrane a signal arising from binding the hormone epinephrine on the extracellular surface of the cell. The common features of the G proteins are presented next. The description of the information-transmission pathway from hormone stimulus to G proteins to adenylate cyclase is completed by a discussion of how cAMP activates specific protein kinases to modulate the activities of the phosphorylated target proteins. A small number of hormone molecules outside the cell results in an amplified response because each activated enzyme in the triggered cascade forms numerous products. There are many distinct seven-helix transmembrane hormone receptors. 

Boeckeler, R, Adley, K., Xu, X., Jenkins, A., Jin, T., and Williams, R S. (2006) The neu-roprotective agent, valproic acid, regulates the mitogen-activated protein kinase pathway through modulation of protein kinase A signalling in Dictyostelium discoideum. Eur. J. Cell Biol. 85, 1047-1057. 

Shih A, Zhang S, Cao HJ, Boswell S, Wu YH, Tang HY, Lennartz MR, Davis FB, Davis PJ, Lin HY (2004) Inhibitory effect of epidermal growth factor on resveratrol-induced optosis in prostate cancer cells is mediated by protein kinase C-alpha, Mol Cancer Ther 3 1355-1364 Siddiqui lA, Adhami VM, Afaq F, Ahmad N, Mukhtar H (2004) Modulation of phosphatidylinositol-3-kinase/protein kinase B- and mitogen-activated protein kinase-pathways by tea polyphenols in human prostate cancer cells. J Cell Biochem 91 232-242... 

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