Chapter 11
Messengers include: neurotransmitters, hormones, cytokines, eicosanoids, and others
1st messenger mentioned
Acetylcholine
Acts similar to a hormone, because it is released and binds to the receptor on the extracellular side of the cell, which is a muscle cell.
Disease Myasthenia Gravis
Antibodies you create bind to this receptor and prevent binding of acetylcholine to the receptors
Autoimmune disease that blocks this receptor at the neuromuscular junction
Three types of signaling
Paracrine
Hormones are effective on nearby cells
Really common in the immune system when potential invasion of bacteria or virus
Neurotransmitters are examples of paracrine signaling
Endocrine
Hormones are released into the bloodstream and exerts its actions on specific target cells throughout the body
Signal released from glands in your body
Autocrine
Act on the same cell from which the hormone was secreted
Small molecule neurotransmitters
Acetylcholine
Gamma aminobutyrate GABA
Epinephrine
Other types of polypeptides
Steroid hormones
Cytokines from the immune system
Chemokines
Systems in the body that use chemical messengers
Nervous system
Ach, epinephrine y-amino butyrat
Endocrine system
Insulin is secreted by beta cells of the pancreas
Polypeptide, catecholamines, steroid, thyroid
Immune system
Chemokines, cytokines
Eicosanoids
Common signaling molecule
Derived from arachidonic acid (20-C molecule that comes from you food esp meat)
Some are prostaglandins
They are released in response to injury in the body
Hormones (first messenger)
Can have cell surface receptors or intracellular receptors
Binding of protein and peptide hormones to cell surface receptors initiates events that lead to the generation of second messengers within the cell
Also known as signal transduction
Receptors for steroid and thyroid hormones are located inside target cells, in the cytoplasm or nucleus and function as ligand-dependent transcription factors
2 ways receptor can signal a cell
Hydrophilic
Hours to effect cell
Binds to receptor on outside of cell and elicits response to inside of cell (doesn’t travel into cell)
Hydrophobic
Minutes to effect cell by entering straight into the nucleus
Go through the plasma membrane and bind by the cytosolic receptor or they can go all the way to the nucleus and bind to DNA there acting as a transcription factor (travels into cell)
Second messengers- One of the initiating components of intracellular signal transduction cascades.
Are intracellular signaling molecules released by the cell to trigger physiological changes such as proliferation, differentiation, migration, survival, and apoptosis. cAMP made when the membrane enzyme adenylyl cyclase is activated by the alpha subunit of a G-protein
ATP loses pyrophosphate and forms cyclic molecule with 3’ and 5’ end from the ribose of ATP
Phosphatidylinositol molecules
Usually phosphorylated 3x and then the phosphatidylinositol is cleaved into diacylglycerol and inositol triphosphate.
Acidic (anionic) phospholipids
Regulate activity of a group of at least a dozen related enzymes known as protein kinase C
Second messengers that include diacylglycerol, inositol triphosphate, cAMP, and GNP all have to be degraded quickly or they will wreak havoc.
Can terminate them through diffusion, desensitization, phosphatation that cleaves phosphates off, phosphodiesterases will cleave bond to regenerate AMP and same with GNP, and GTPases which will hydrolyze GTP and turn signal on.
Insulin receptor
Really good example of the receptor that has autophosphorylation capabilities
Belongs to the tyrosine kinase family
Serpentine receptors
G-protein coupled receptors
Signal binds alpha subunit dissociates and exchanges GDP for GTP
Associates with another integral membrane protein such as adenylyl cyclase (important for formation of cAMP)
GTP on alpha subunit is hydrolyzed and activates adenylyl cyclase to make cAMP from ATP
Then the alpha subunit of the heterotrimeric G protein travels
