Extracellular Hormone Flashcards
List plasma protein membrane receptor ( 2nd messenger) types and examples and their synthetic paths
1 peptide - insulin / glucagon. Proteolytic processing of prohormone
2 eicosanoid - PGE. From arachidonate
3 catecholamine - epinephrine. From tyrosine
List nuclear receptor ( 2nd messenger) types and examples and their synthetic paths
1 steroid - testosterone. From cholesterol
2 thyroid - T3/ triidothyromine. From Tyr in thyroglobulin
3 retinoids - retinoic acid. From vitamin A
4 Vitamin D - 1,25 dihydroxycholecalciferol. From cholesterol
List cystolic receptor ( 2nd messenger) types and examples and their synthetic paths
Nitric oxide - nitric oxide. From arginine + O2
List the 6 steps of cell to cell communication
1 signal cell produces signal molecule 2 release of signal molecule 3 transport of signal molecule 4 binding of signal molecule to receptor 5 cellular response 6 removal of signal and termination of cellular response
What is cellular response and what causes it
- change in cellular metabolism , function and morphology
- ligand receptor complex
List types of receptors
1 seven membrane transmembrane protein
2 enzyme linked receptor
3 intracellular receptor
4 ion channel receptor
How does a ion channel receptor function and its outcome
- ligand binds to receptor causing conformational changes and this allows specific ions to pass through
- causes change in membrane or cytosolic ionic conc
Describe how a tyrosine kinase linked enzyme works
- binding of ligand causing 2 receptors to form cross link dimer
- the tyrosine of opposite receptors phosphorylate each other
- activated tyrosine acts as docking platforms for diff proteins which are phosphorylated and activated
- signal transduction into cytosol
What does a kinase have the ability to do
What type of proteins bind to tyrosine kinase receptor
-transfer of phosphate from high source substrate
/those with SH2 receptor
Why are tyrosine kinase receptors in pairs
Describe structure of g coupled protein receptor
- so that they can cross phosphorylate each other
- 7 helical proteins transmembrane and with C terminal in cytosol and N terminal in extra cellular domain
List the protein needed for 2nd messenger system
1 hormone receptor
2 G protein
3 adenylate Cyclase
What is transduction
-conformational changes triggered by formation triggered by ligand receptor complex
Property of g property
What is 2nd messenger
- able to bind to guanine triphosphate
- substrate released into cyto after receptor activation
How is cAMP made and by what
-by adenylate cyclase wc is uses ATP as substrate after activated by G protein
List 2nd messengers and type of hormones that utilize the system
cAMP - epinephrine, calcitonin , FSH
Protein kinase activity - oxytocin ,insulin
cGMP - nitrogen oxide
Calcium or / and phosphoinosites - epinephrine, GnRH , thyroid releasing hormones
How does 2nd messenger amplify hormone
- single hormone binds to single receptor
- numerous G proteins activated
- each stimulates numerous adenylate cyclases
- 2 cAMP active a protein kinase
- each PK phosphorylates numerous proteins
How is signal terminated and what happens
- phosphatase 1 removes phosphate groups from diff enzymes
- cAMP is continuously degraded and when hormone dissociates from receptor cAMP levels drop
Describe how R-triggered hydrolysis of phosphatidyl inositol 4,5 biphosphate ( PIP2 ) occurs
- active G protein activates phospholipase wc hydrolyses PIP2 into DAG and IP3 ( both 2nd messengers
- DAG actives PKC and IP3 forms channels at ER to releases Ca and both cause response in target cell
What does DAG and IP3 stand for
What does PKC do
Where is PIP2 found
- diacyglycerol
- inositol triphosphate
-phosphorylates Ser and threonine of certain target cells
/in cell membrane
How is hormonal response regulated
What does GAP do
What does GEP do
-by slowly cleaved GTP to GDP by G protein
/ gtpase activating protein ( GAP ) assist in GTP cleaving
- guanine exchange factor aids in transfer of GDP to GTP on G protein
What does Gi do and how
/it responses to adenylate inhibition by binding to it and decrease cAMP synthesis
Describe G protein cycle
-inactive G protein has GDP changed to GTP by GEF due to bound receptor and is now active
/active G protein actives adenylate with the aid of GAP via alpha adenylate cyclase complex
-g protein now has gdp but adenylate active and complex dissociates
-g protein reacquires beta and gamma subunits and now inactive
Describe mechanism of coupling by cholera toxin and its effects
/cholera has 2 peptide chains ( A and B )
- B bind to membrane and A enters cell and catalyses transfer of ADP ribose for NAD plus to G protein
- product is ADP ribosyl GTP protein + water and nicotiamide
- ADP ribosyl is a covalent modification preventing hydrolysis to GDP and go protein kept in active state leading to influx of water and Na in gut
Examples of effects of cAMP
- in adipose actives PKA to stimulate more fatty acid production
- in ovarian cycle PkA stimulated to produce more estrogen
Describe mechanism of g coupled protein
- ligand binds to receptor causing conformational change to receptor and it reacts with g Protein to change GDP to GTP
- actives AC
- AC create cAMP
- cAMP active PK which phosphorylate proteins to activate them
- cellular response
