Mitogen-activated protein kinase system

Two processes have been proposed to explain the mitogenic effect of fluoride on bone cells involving either fluoride ions directly or the AIF complex (Fig. 11). Fluoride ions have been shown to directly inhibit an enzyme (tyrosine phophory-lase phosphatase) resulting in an enhancement of the tyrosine phosphorylation part of the mitogen-activated protein kinase system (MARK) [177], The other activation pathway involves a complex of aluminium and fluoride which activates the G-protein and stimulates tyrosine phophorylation resulting in an enhanced mitogenic effect [176]. 

CBi and CB2 seem to couple to inhibitory Gj and/or G0 proteins. CBi receptors are known to effect adenylate cyclase, a variety of potassium and calcium currents, and the mitogen-activated protein kinase pathway. CBi receptors have been shown to activate at least six subtypes of Gj and G0 proteins, supporting reports that they effect a wide variety of intracellular signaling systems. In contrast to CB receptors, CB2 receptors do not seem to effect ion currents directly (Breivogel et al., 2001). 

Pullarkat SR, Mysels DJ, Tan M, Cowen DS. Coupling of serotonin 5-HT1B receptors to activation of mitogen-activated protein kinase (ERK-2) and p70 S6 kinase signaling systems. J Neurochem 1998 71 1059-1067. 

Ashwell, J.D. (2006). The many paths to p38 mitogen-activated protein kinase activation in the immune system. Nat Rev Immunol 6, 532-540. 

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