Cell Signaling: Receptors, Ligands, and Signal Transduction Pathways

Acetylcholine

Transmitter found on plasma membrane of skeletal cells and behaves as chemically gated sodium ion channel

Chemically Gated Ion Channels

Open to let specific ions (Na+) to pass through the membrane in response to the binding of a ligand (neurotransmitter)

Enzyme Coupled Receptors

Act as enzymes or they associate with enzymes found inside of cells

Receptor Tyrosine Kinases (RTK)

Are the most common enzyme coupled receptors and influence cell cycle, migration, metabolism, and division

Extracellular ligand binding domain

Part of RTK that faces extracellular fluid and binds ligand

Intracellular kinase domain

Part of RTK that faces cytosine and consists of many amino acids (Tyrosine)

Dimerization

When two RTKs are brought together

Autophosphorylation

When Tyrosine is phosphorylated

Importance of RTKs coming together

Cells won't be able to divide if they do not

Insulin

Hormone produced by B cells of pancreas (long lived)

Insulin Receptor

Activated by insulin which lowers blood glucose

Phosphatases

Enzymes that dephosphorylate phosphorylated proteins (removes phosphate groups)

Kinases

Adds phosphate groups

Kinase Cascades

Series of protein kinases that phosphorylate each other in succession

MAP

Mitogen activated protein

Signal amplification

When one signal is made bigger using kinases

Ras

GTP binding protein that stimulates cell division and activates MKKK (MAP kinase kinase kinase)

G protein coupled receptors (GCPR)

Most common membrane receptors that consist of 7 alpha helix's that is active when alpha subunit is bound to GTP and inactive when it is bound to GDP

Adenylyl cyclase

Found on plasma membrane and is active when GTP bound alpha subunit protein binds to it producing cyclic AMP (cAMP)

cAMP

Second signaling messenger that originates inside of the target cell

Ligand

First/primary messenger which originates outside of signaling cell

Adrenaline

Hormone produced by adrenal glands

Three responses to adrenaline

Increased heart rate, breakdown of glycogen to glucose in skeletal muscles, breakdown of fats to fatty acids in fat cells

Phospholipase C

Cuts PIP2 into IP3 and DAG (second messengers)

IP3

A second messenger that opens Ca2 channel and releases Ca2 (second messenger)

Epinephrine

Produced by adrenal glands that stimulates liver cells to breakdown glycogen to glucose 6 phosphate

Glucagon

Produced by 2 cells of pancreas that stimulates liver cells to breakdown glycogen to glucose 6 phosphate

Location of glucagon & epinephrine

Plasma membrane of liver cell

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