Regions closest to the phagosome (R1 and R2) exhibited significantly elevated cAMP (Figure 4A and D).
Elevated cAMP resulted in dissociation of the subunits, and a resulting graded loss of FRET signal.
These results suggested that stimulation of EphA receptors elevated cAMP levels.
Interestingly, elevated cAMP levels and hyperactivation of PKA have been implicated in T cell anergy and dysfunction [63].
Elevated cAMP level suppresses the activity of immune, inflammatory, and epithelial lung cells and inhibits airway remodeling [10].
Reduced invasiveness and elevated cAMP levels were accompanied by decreased MMP-9 as well as lowered RhoA activity [4].
In most of the cells originating from the neuroectoderm including the neural crest, elevated cAMP levels result in ERK activation, through B-Raf activation [6], [10], [32].
cAMP serves as a negative regulator of phagocyte function [10] and elevated cAMP levels are associated with suppression of innate immune functions including the production of pro-inflammatory mediators, phagocytosis, and microbial killing [5].
Correlating with the Gs coupling, acute morphine induced elevated cAMP levels and a several-fold increase in pS133CREB that were also completely blocked by NLX, NTX or the FLNA pentapeptide.
As discussed in more detail below, one attractive explanation for these observations is that SDF1 induced activation of PLC indirectly induces elevated cAMP levels through a separate mechanism from the more traditional direct activation of adenylate cyclases by Gαs.
Finally, based on the fact that many of these ATR responsive endocrine targets are downstream of both SF-1 and cAMP signaling, we propose that the selective effects of ATR in endocrine cell types are mediated by convergent regulation of NR5A receptors and elevated cAMP.
