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Cell Signaling Dr. L

Cell signaling

What is the agonist? the primary signal that interacts with some type of receptor system. in some cases it can be the cell
What does the receptor signal lead to? Some chemical cascade of events which leads to a biological response
Name some biological responses contraction, relaxation, secretion, transcription, translation, vision and hearing
True or False: Agonist have different effects depending on what cell they are interacting with True. Ex. smooth muscle: NO relaxes muscle. Platelets, NO inhibits activation
Mast cell example Once activated releases histamine and heparin sulfate that causes vasodilation of smooth muscle cells and in endothelial cells vascular permeability
If there is tissue injury what do mast cells do? Degranulate which increases vasular permeability allowing fluid to get into the underlying tissue. ex. neutrophils
True or False: Agonist can be soluble, extracellular matrix associated proteins (collagens) or cell associate cell to cell interactions True
What is a good example of cell to cell interactions C-kit of stem cells and steel factor of adventia cells
Describe autocrine A molecule that acts as a primary signal and feedsback onto the same cell
Describe panacrine A signal that is released from a cell and interacts with receptors on neighboring target cells
Describe endocrine A product that is being released and uses the vasculature and then binds to a receptor on a target cell
What are most receptor cells? Proteins. they can be glycolipids
Do receptors have specificity? yes, they bind a specific extracellular signal molecule and initiates a response in a cell
What is saturability? When you have a limited number of responses
What is signaling ability? When you induce signal transduction. A receptor is defined as a protein or glycolipid that will bind an external signal
Are cell surface receptors hydrophillic? Yes because it can't get through the lipid bilayer. It binds a plasma membrane receptor and that initiates a signal transduction response
Are intracellular receptors hydrophillic? No they are lipophilic or hydrophobic
Name some lipophilic moleucles Steroids: Cortisol, estradiol, testosterone, thyroxine, Vitamin D
What type of factors are the intracellular receptors? Transcription factors. They tend ot have ligand binding and DNA binding domains
Do the receptors exist in an inactive or active conformation? inactive. The signal binds to the ligand binding pocked and causes conformational change allowing the receptor to interact with DNA binding elements
compare effect of acetylcholine in cardiac muscles, skeletal and salivary glands Cardiac: Decreased rate of contraction. Skeletal: increased contraction. Salivary glands: induced secretion
Describe ion-channel linked receptors Allow ions to come down concentration gradient when opened
Describe ligand gated channels Ligand has to bind to channel and then ions come down conentraion gradient
Describe voltage gated channels Due to depolarization the channel opens up
describe mechanical gated channels Stretch a cell and it could lead to opening
What happens in a channel in series? Depolarization can be propogated down a very long distance. One opening leads to opening of adjacent channel
Where is the primary signal from typically? From the outside of the cell and it can generate a second messenger to move the biological signals forward
What is crosstalk? When you activate one system and that can activate multiple things
Name components of a G-protein coupled system Receptor, coupling protein, and enzyme (in that order)
How many transmembranes do G-protein coupled receptors have? 7
Name the 3 subunits of Heterotrimeric g-proteins alpha, beta and gamma
when GDP comes off of H. G-proteins what stays together out of the subunits? beta and gamma. and the alpha is free (GTP receptor itself)
Describe the adenyl cyclase system Receptor activate a G protein, alpha activates adenyl cyclase,Takes ATP and makes cyclic AMP, activates Protein Kinase A, cAMP bings to regulatory subunits and frees catalytic subunits
Name a couple of residues Serine, threonines and tyrosines
True or False: Kinases put on phosphate and phosphatases remove phosphate True
True or False: Enzymes that can phosphorylate tyrosine can only phosphorylate tyrosine True
Can enzymes that phosphorylate serine also phosphorylate threonine yes and vice versa
When you phosphorylate something do you have to dephosphorylate it? Yes, turn it on you have to turn it off. Remove the signaling molecule from receptor or desensitize receptor: Endocytosis
What does phospholipase C target? Phophatidylinostiol. It will hydrolyze it leading to the generation of two potent secondary messengers: inostiol trisphophate (IP3) and diacyglycerol
What does IP3 bind to? To receptors on the endoplasmic reticulum that will open up a channel which allows calcium to come out to activate kinases, calmodulin etc.
Plug and Play Model Epinephrine, adrenergic will activate Gs which is specific G-protein that will activate adrenylate cyclase and increases cAMP
What do you think of anytime you see a tyrosine kinase? Growth
What does thrombin do in the plug n play model? comes in and cleaves the whole terminal segment of the receptor which leads to activation of receptor
What are the 3 domains of the receptors? ligand binding, transmembrane and internal catalytic
What does tyrosine kinase activate? Ras which is a monomeric GTP binding protein that lives at the plasma membrane because it has an isoprenylation group.



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