Second Messengers

The membrane receptors that induce second messengers are GPCRs of GPCR families. Stimulation of the guanine nucleotide-binding protein-coupled receptors leads to signal transduction of sensory, hormonal, or photic stimuli into regulation of effector enzymes and ion channels. Signal transduction is accomplished through the coupling of G-proteins, via second messengers, to various secondary pathways involving ion channels, adenylyl cyclases, and phospholipases. Further, GPCRs may also couple to other proteins, such as those containing PDZ domains. GPCRs are diverse and of ancient evolutionary lineage, and are found in fungi, plants, and animals.

Messenger

Stimulator

Enzyme

Acts on

cAMP

Adrenaline, glucagon, luteinizing hormone (LH), parathyroid hormone (PTH), adrenocorticotropic hormone (ACTH) adenylyl (adenylate) cyclases

cAMP-dependent protein kinase, (PKA),

gene transcription

cGMP

Photic response of retinal rods (rhodopsin), nitric oxide (NO), atrial natriuretic peptide (ANP), guanyl cyclase protein kinase G (PKG)

diacylglycerol (DAG)

growth factors phospholipase C-gamma protein kinase C (calcium dependent)

Inositol-1,4,5-trisphosphate (IP3)

growth factors phospholipase C-gamma

protein kinase C (calcium dependent)

Ca2+ ions

Voltage-gated channels – after depolarization by an action potential; receptor-operated ion channels in post-synaptic membranes, which open upon nt-binding; GPCRs muscle contraction, neurotransmitter release at neuronal synapses (LTP, LTD), secretion of hormones, apoptosis, cell adhesion to extracellular matrix, T/B cell activation neurotransmitter release at neuronal synapses, secretion of hormones, apoptosis, cell adhesion to extracellular matrix, activation of T and B cells
 Cell signaling  Receptor Tyrosine Kinases(RTK)  Second Messengers  Phosphate-handling Enzymes  · adenylyl (adenylate) cyclase · calcium ion · calcium ions · cAMP-dependent protein kinase · CDKs · cyclin-dependent kinases · DAG · diacylglycerol · DNA ligases · ERKs· GPCRs · GPCR families · guanylate cyclases · guanyl cyclase · inositol triphosphate · IP3 · MAP kinases · mitogen activated protein kinases · phosphatases · phosphodiesterases · phospolipases · phosphorylation · PKA · PKC · phospholipase C-gamma · protein kinase A · protein kinase C · protein tyrosine kinases (PTKs) · receptor tyrosine kinases · second messengers · second messenger cAMP · second messenger cGMP · signal transduction · two-component systems ·

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