Karteikarten
Lecture 24 - Cell Signalling (2)
Karten in diesem Stapel (24)
- 1What is vasopressin?An antidiuretic hormone; increases ion and water uptake from nephrons - returns them to blood; reduces urine volume
- 2What is process for vasopressin?1) Vasopressin binds GPCR
2) G protein alpha activate adenylyl cyclase (AC)
3) cAMP activates protein kinase A (PKA()
4) PKA induces movement of vesicles containing aquaporins to move to plasma membrane - 3What does smooth muscle contraction use as secondary messengers?IP3 and Ca2+
- 4Process for smooth muscle contraction?1) Kinases add phosphate groups to phosphatidylinositol to make PIP2
2) Activation of acetylcholine receptor (a GPCR) by acetylcholine
3) GP-alpha activates phosphatidylinositol-specific-phospholipase C-B (Pl-PLCB)
4) Pl-PLCB splits PIP2 into DAG and IP3
5) IP3 diffuses into cytosol
6) IP3 binds to an IP3 receptor (a ligand gated Ca2+ channel) in the membrane of the SER
7) Binding of IP3 to receptor releases Ca2+ and triggers muscle contraction - 5What are the two main ways signaling works?1) Activation of receptor activates an effector protein, then soluble second messenger into cell, triggers signal cascade leading to cell effects
2) Activation of the receptor forms a 'recruiting station' that in turn recruits other proteins. triggering signal cascade - 6What are receptor tyrosine kinases? (RTKs)Receptors function as enzymes
-Receptor tyrosine kinases phosphorylate target proteins (including themselves) at particular tyrosines
-Single transmembrane segment - 7What are RTKs involved in regulation of?Growth, cell division, cell survival and death, cell attachments, migrations, insulin perception and response
- 8How do RTKs function as dimers?Binding of ligand induces dimerization either by:
-One ligand binding to both monomers or
-One ligand binds to each monomer, causing them to dimerize - 9How do RTKs phosphorylate one another?The two monomers, once joined moves aa loops out of way, exposes kinase domains. Then kinase domains transautophosphorylate each other. One phosphorylate each other, they are activated and can bind to other signaling molecules
- 10How can RTKs work differently once activated?Ex) SH2 domain of Grb2 (docking adaptor) binds phosphorylated tyrosine on the receptor, other domains of Grb2 have Sos and Ras bound to it... now associated with receptor.
Ex2) IRS binds to receptor which further phosphorylates tyrosines on IRS, these serve as docking sites for other proteins
Can also do direct phosphorylation and recruitment of transcription factors which will then get transported to nucleus. Also direct recruitment of other signaling proteins - 11What is an epidermal growth factor (EGF)? What does it do?Growth factor (or cytokine) that plays important role in regulation cell growth, proliferation & differentiation by binding to its receptor epidermal growth factor receptor (EGFR)
-This signaling results in changes in gene expression
-Transcription factors are activated - genes involved in cell proliferation such as the cyclins are transcribed - 12What do mutations leading to EGFR overexpression cause?Cancers, including lung cancer
- 13What is MAP kinaseMitogen activated protein kinase - serine/threonine specific kinases. They are chemical substances that induce mitosis (EGF is ex)
- 14How does EGF activated MAP kinase pathway?1) EGF binds and activates EGFR
2) EGFR autophosphorylates its tyrosines
3) Phosphorylated tyrosines serve as docking station for Grb2/Sos, which is recruited to the membrane
4) SOS is a GEF that activates Ras
5) Ras recruits a threonine/serine kinase called Raf
6) Raf phosphorylates and activates MEK
7) MEK phosphorylates and activates ERK
8) ERK phosphorylates transcription factors which enter nucleus and start transcription of target genes that initiate the cell cycle (e.g. cyclin D) - 15What is Ras?Monomeric G-protein embedded in membrane by lipid group, active when bound to GTP, inactive with GDP
- 16What is Grb2?Acts as adaptor protein that links EGFR and Sos
- 17What else can MAP-kinase pathway do?In yeast can regulate yeast mating and osmoregulation, plants it regulates response to pathogens, in flies regulates dev of photoreceptors
- 18How and when can Calcium enter cell?By voltage dependent channels in nerves, some muscles and receptor-mediated calcium channels
-Fertilization - channels will open up in oocytes after fertilization so will prevent sperm entry anywhere around the large cell, begin activation of cyclins for cell division
-Calcium can also bind to calmodulin which modulates activity of other pathways such as adenylyl cyclase and other kinases - 19How can nitric oxide act?Inorganic gas - extracellular messenger and second messenger
-Synthesized by NO synthase within cells with Arg as substrate, acts as autocrine and paracrine hormone
-Activates guanylyl cyclase to make cGMP - 20What happens with NO in blood vessels?Acetylcholine can produce NO synthase, cGMP causes smooth muscle cells to relax, nitroglycerine applied under tongue to patients with congestive heart probs, produces NO to relax arteries
- 21Drugs to inhibit cGMP phosphodiesterase do what?Breaks down cGMP to GMP used for relaxing blood vessels, e.g. viaga
- 22What is convergence?Two receptors cause the same secondary signal to be activated
- 23What is divergence? Ex?One ligand has several effects or one signal propagates several responses - e.g. PKA (induced by epinephrine receptor) turns on 3 different proteins
- 24What is crosstalk? Ex?Pathways interconnect - cell receives combo of signals that can trigger different pathways, each step provides opportunity for crosstalk b/w signals, through cross talk the cell integrates info from different signaling pathways to initiate appropriate response
-ex: epinephrine can counter affect of growth factor because PKA inhibits Raf
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- Cell Biology Karteikarten am Lecture 24 - Cell Signalling (2), erstellt von Emma Granger am 09/04/2018.
- Erstellt von
- Emma Granger · Apr 2018
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- 9 Apr 2018
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