Subtypes signal activation

Retinoic acid (RA), forskolin, and HDAC inhibitors have been shown/used to induce neuronal differentiation of hippocampal adult neural progenitor cells. However, these factors are either pleiotropic or of undefined physiologic relevance RA has neuronal subtype patterning activity and also been reported to induce cardiac differentiation (27) as well as pancreatic differentiation (28) HDAC inhibitors are nonspecific and forskolin activates protein kinase A and serves to increase the cellular levels of the general signaling molecule cAMP (29). 

At a cellular level, the activation of mAChRs leads to a wide spectrum of biochemical and electrophysiological responses [1, 5]. The precise pattern of responses that can be observed does not only depend on the nature of the activated G proteins (receptor subtypes) but also on which specific components of different signaling cascades (e.g. effector enzymes or ion channels) are actually expressed in the studied cell type or tissue. The observed effects can be caused by direct interactions of the activated G protein(s) with effector enzymes or ion channels or may be mediated by second messengers (Ca2+, DP3, etc.) generated upon mAChR stimulation. 

The PAR-3 subtype of the PAR family is truncated at the C-terminus limiting its potential to signal intracel-lularly. Furthermore, other than thrombin, there have been no specific activating peptides developed that... 

M2 subtype modulates the amount of REM sleep. If postsynaptic muscarinic receptors of the M2 subtype contribute to REM sleep generation, then pharmacological manipulation of M2-activated signal transduction cascades would be anticipated to alter REM sleep (1.2 on Fig. 5.1). 

Dopamine receptors are found primarily in brain, although they also exist in kidney [33]. Two subtypes of dopamine receptor were initially identified based primarily on differences in their drug specificities and signaling mechanisms. D receptors were found to stimulate adenylyl cyclase activity, while D2 receptors inhibited this enzyme (Fig. 12-6). Subsequently, multiple Dr and D2-like receptors were identified by molecular cloning (Table 12-3) [33], All dopamine receptor subtypes are... 

CREB is also phosphorylated on serine 133 by stimulation of growth factor signaling cascades [63]. This occurs via a complex pathway involving MAPK cascades (Fig. 23-9). Thus, as outlined earlier, nerve growth factor and related neurotrophins that act on receptor tyrosine kinases lead to the successive activation of Ras, Raf, MEK and ERK. Activated ERK then phosphorylates and activates a serine-threonine kinase, RSK, particular subtypes of which directly activate CREB via the phosphorylation of serine 133. 

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