SIGNAL transduction

Question 1

What are the two major classes of hormones?

Answer 1

Group 1 hormones (steroids, iodothyronines, calcitriol, retinoids) bind their receptor in the cytoplasm, form a dimer, move into the nucleus and bind DRE. Group 2 hormones (polypeptides, proteins, glycoproteins, catecholamines) start their signaling through membrane receptors. DRE (DNA hormone responsive elements)

Question 2

What are the second messengers for group 2 hormones following receptor activation.

Answer 2

1) – cAMP 2) - cGMP-atrial naturetic factor, nitric oxide 3) calcium or phosphatydlinositol or both 4)-kinase or phosphate cascade eg: 1 Alpha2 adrenergic catecholamines, beta-adrenergic catecholamines, ACTH, ADH (vasopressin), calcitonin, chorionic gonadotropin, corticotropin-releasing hormone, follicle-stimulating hormone, glucagon, lipotropin (LPH), luteinizing hormone, melanocyte-stimulating hormone, parathyroid hormone, thyroid-stimulating hormone (TSH). 3 acetylcholine (muscarinic), Alpha 1-adrenergic catecholamines, angiotensin II, antidiuretic hormone, cholecystokinin, gastrin, gonadotropin releasing hormone, oxytocin, platelet derived growth factor, substance P, thyrotropin releasing hormone. 4 adiponectin, chorionic somatomammotropin, epidermal growth factor, erythropoietin, fibroblast growth factor, growth hormone, insulin, insulin-growth factors 1 and 2, leptin, nerve growth factor, platelet-derived growth factor, prolactin

Question 3

What are the hormones that act through cAMP?

Answer 3

The receptor for this group is the CGMPR family secretin like which uses various G proteins (Gas) to activate/deactivate adenylate cyclase as well as cause calcium release. Alpha2 adrenergic catecholamines (Gi), beta-adrenergic catecholamines(Gq,i,s), ADH (vasopressin) > AVPR2, calcitonin>CALCR> (Gs,q), lipotropin (LPH), luteinizing hormone, melanocyte-stimulating hormone, parathyroid hormone(Gs), chorionic gonadotropin, ACTH, corticotropin-releasing hormone, follicle-stimulating hormone, glucagon, thyroid-stimulating hormone (TSH).

Question 4

What are some hormones that act by affecting ion channels > increasing calcium levels, and/or activating phosphoinositide phospholipase C?

Answer 4

Ligands for rhodopsin like GPCR’s release an alpha unit (Gaq11) which activates phospholipase C, which cleaves PIP2, releasing IP3 which opens calcium channels, and DAG, which attracts PKC to the cell membrane. Examples include: acetylcholine (muscarinic), alpha 1-adrenergic catecholamines, angiotensin II, oxytocin, platelet derived growth factor (PDGF), substance P, antidiuretic hormone (ADH), cholecystokinin (>CCKAR and CCKBR), gastrin (>CCKBR), gonadotropin releasing hormone (GnRH > GnRHR), thyrotropin releasing hormone (TSH > TSHRH). AVPR1A (arginine vasopressin receptor 1A) CCKAR (cholecystokinin A receptor, CCK1, CCKA) CCKBR (cholecystokinin B receptor, CCK2, CCKB, gastrin receptor, also responds to gastrin) DAG (diacylglycerol) GnRHR (gonadotrophin releasing hormone receptor) IP3 (inositol triphosphate) NK1R (neurokinin 1 receptor) PIP2 (phosphatidylinositol 4-5-biphosphate) PLC (phospholipase C) PKC (protein kinase C)

Question 5

What are some hormones that act by stimulating a kinase or phosphate cascade?

Answer 5

adiponectin, chorionic somatomammotropin, epidermal growth factor, erythropoietin, fibroblast growth factor, growth hormone, insulin, insulin-growth factors 1 and 2, leptin, nerve growth factor, platelet-derived growth factor, prolactin

Question 6

How do interleukin receptors work?

Answer 6

The extracellular components are immunoglobulin like and the intracellular end shares a TIR motif. IL-1 receptors and TLR receptors then bind MYD88, TRAF3, TRAF6, IRAK resulting in the generation of transcription factors NF kB and AP1. TIR (Toll IL-1 Receptor) TRAF1 (TNF receptor-associated factor 1) IRAK1 (interleukin-1 receptor-associated kinase 1) AP-1 (activator protein 1), part of a heterodimeric protein which may include C-Fos, C Jun.

Question 7

Are interleukin receptors specific for a single interleukin?

Answer 7

No. The same receptor responds to IL-1 and IL-18, another to either TLR5, TLR7, TLR9, and TLR11; separate ones for TLR2, TLR4, TLR3. Depending on the combination, NF-kB, AP1, IRF3, IRF7, may be generated.

Question 8

How does the adiponectin receptor work?

Answer 8

This receptor is oriented with cytoplasmic N terminus, extracellular C terminus (opposite to G protein coupled receptors) and does not associate with G proteins. Activates AMPK and PPAR-a. PPARa (peroxisome proliferator activated receptor alpha)

Question 9

Name some promiscuous ligands and receptors.

Answer 9

Promiscuous ligands include: acetylcholine (nAChR-nicotinic-ligand gated ion channel, mAChR, muscarinic, G protein coupled receptor, alpha unit deactivates adenylate cyclase, decreasing cAMP ), adrenergic stimulation activates 2 alpha receptors, and 3 beta receptors (all GPCR), arginine vasopressin receptors-3, Promiscuous receptors include: IL1R1 (interleukin 1 receptor 1 binds IL-1 alpha and beta, and IL1RA)

Question 10

What peptide chains constitute the receptors for IL-1,2, and 5?

Answer 10

Interleukins 1, 2, and 5 rely on CD coreceptors. IL-1 uses CD121a (IL1R1) along with IL1RaP (IL-1 accessory Protein) transmits signal. CD121b (IL1R2) is a decoy receptor that binds IL-1 alpha and beta but no signal results. IL-2 uses CD25 (IL-2Ralpha), CD122 (IL-2Rbeta), CD132 (IL2Rgamma), and beta subunit CD131 (CSF2RB). IL-5 receptor is CD125 (IL5RA) and beta subunit CD131 . These receptors transmit a signal due to ability to bind JAK kinase which is activated by receptor aggregation after ligand binding. IL1RA is the product of the gene IL1RN and is a decoy ligand. CD131 (CSF2RB, granulocyte-macrophage colony-stimulating factor receptor, beta).

Question 11

How are G protein coupled receptor classified?

Answer 11

GRAFS classification system for GPCR receptors is by ligand - Glutamate (22 genes), Rhodopsin like (662), Adhesion (33), Friizzled (11) / Taste2 (25), and Secretin (15). Rhodopsin like receptors are a superfamily (evolutionarily linked but no longer share sequences) of 19 subtypes (639) + non catagorized types (23).

Question 12

How are the main proteins responsible for signal transduction classified?

Answer 12

Cell signaling protein (types) are separated into Intercellular (4), cell surface(8), and intracellular (3). Calcium signaling, and lipid signaling involve all 3 varieties. Intercellular-neuropeptides, growth factors, cytokines, hormones cell surface protein receptors-ligand gated, enzyme linked, G protein coupled, immunoglobulin superfamily, integrens, neuropeptide, growth factor, cytokine intracellular- adapter proteins, GTP binding, map kinase, calcium signaling-ion pumps, cell membrane calcium channels, adhesion molecules lipid signaling - eicosanoids, lysophospholipids, steroids, others.

Question 13

What are the main enzyme linked cell surface receptors?

Answer 13

Serine/threonine-specific protein kinase, receptor tyrosine kinase, guanylate cyclase

Question 14

What are type I and type II cytokine receptors

Answer 14

Type I cytokine receptors respond to cytokines with four alpha helical strands. Receptors share common traducing chains namely: 1) gamma chain (CD130) IL-6 IL-11, IL-12, leukemia inhibitory factor, oncostatin M receptor. 2) common beta chain (CD131) GM-CSF receptor, IL-3, IL-5, and gp230 3) CD132; IL-2, IL-4, IL-7, IL-9, IL-13, IL-15, Upon ligation these chains result in JAK kinase phosphorylation and signal transduction. Type II cytokine receptors bind type I and type II interferons as well as IL-10, IL-20, and IL-22. They have variable immunoglobulin extracellular components and intracellular proline rich region that attract different Jak kinases. JAK1 and TYK2 for type 1 cytokines, and JAK1 and JAK2 for type 2 cytokines (IFN gamma).

Question 15

What lipid products play a role in signaling?

Answer 15

Lipid products that play a role in signaling will include actiators of 1) phospholipase C phosphatidylinositol biphosphonate (PIP2), 2) G-protein coupled receptors: lysophosphatidic acid, sphingosine-1-phosphate, platelet activating factor (PAF), endocannabinoids, prostaglandins, retinol derivatives. 3)nuclear receptors: Steroid hormones, retinoic acid, prostaglandins.

Question 16

What are the biogenic amines that target she protein coupled receptors?

Answer 16

Biogenic amines that target a G protein coupled receptor include monoamines-histamine, serotonin, , catecholamine (norepinephrine, epinephrine, dopamine) and various trace amines.

Question 17

How many types of enzyme linked surface receptors are there?

Answer 17

Enzyme linked surface receptors include receptor protein serine/theonine kinase-3 types Tyrosine kinase receptor families - 16+ types Serine/theonine kinase receptors include bone morphogenic protein receptor 3, anti-Mullerian hormone receptor. Tyrosine kinase receptor families including receptors for: EGF, insulin receptor, PDGF receptor, FGF receptor, HGF (hepatic growth factor), TRK receptor, EPH (ephrin), LTK (leukocyte receptor tyrosine kinase), TIE (Angiopoietin), ROI (receptor tyrosine kinase-like orphan receptor), DDR (discoidin domain receptor), PTK7 (tyrosine-protein kinase-like 7), RYK (related to receptor tyrosine kinase), MuSK (muscle-specific kinase), ROS (proto-oncogene tyrosine-protein kinase), AATYK (apoptosis-associated tyrosine kinase), AXL (tyrosine-protein kinase receptor UFO) + unclassified.

Question 18

What proteins are involved in producing NF-kB1 by stimulating the IL-1 receptor?

Answer 18

IL-1 stimulates the transmembrane receptor IL-1R, which has many associated proteins including IL-RAcP, MyD88, IRAK and TRAF6. MyD88, IRAK and TRAF6 also associate with Toll like receptors. These complexes stimulate NIK which then phosphorylates IkB-alpha (inhibitor of kappa B) which is then ubiquinated and destroyed releasing bound p65 (RelA) and NF-kB1 (p50) which work as a heterodimeric transcription factor for inflammatory response (~150) genes. IL-RAcP IL-1 receptor accessory protein MyD88 myeloid differentiation primary response gene 88 IRAK IL-1 receptor-activated protein kinase TRAF tumor necrosis factor receptor-associated factor NIK NF Kappa B-inducing kinase, MAP3K14

Question 19

How does TGFbeta become an active ligand?

Answer 19

TGFbeta is a member of a superfamily which includes inhibins, activin, anti-mullerian hormone, bone morphogenic protein, and decapentaplegic. It is expressed by 3 genes in many cells and exists on the surface in a complex that is released through plasmin activation. Further enzymatic action is necessary to cleave the complexed ligand which dimerizes producing a 25 kDa active ligand.

Question 20

What is the role of PKC in GPCR activation?

Answer 20

PKC is a serine/threonine kinase in 15 isoforms in different tissues which is stimulated by DAG to phosphorylate multiple substrates which then lead to smooth muscle contraction or other downstream effects. PKC is active much longer than GTP remains bound to Ga subunit of the homotrimeric G protein. PKC- protein kinase C DAG- diacylglycerol

Question 21

How does the TGF beta receptor work?

Answer 21

TGF beta receptor 2 (gene TGFBR2) binds TGF dimer, attracts TGF beta receptor 1 (TGFBR1) which activates serine/threonine kinase to phosphorylate R-SMAD leading to transcription factor activity. Endoglin is transmembrane glycoprotein that binds to TGFBR1,2,and 3 but not the ligand, and modifies downstream effects. TGF transforming growth factor beta R-SMAD receptor activated SMAD endoglin CD105 important in angiogenisis, neoplasia

Question 22

How many nuclear receptor ligand’s are there?

Answer 22

9, CAR, FXR, LXR, PPAR, PXR, RAR, RXR, SHR, And TR. CAR (Constitutive Androstane Receptor) recognized by endobiotic and xenobiotic substances. FXR (farnesoid X receptor, NR1H4) responds to bile acids. LXR (liver X receptor, regulates cholesterol, fatty acid, and glucose homeostasis) PPAR (peroxisome proliferator-activated receptor, regulates cellular differentiation, development, and metabolism) PXR (Pregnane X receptor, SXR, NR1I2, response to steroid and xenobiotic sensing) RAR (retinoic acid receptor) RXR (retinoid X receptor, heterodimerizes with CAR, FXR, LXR, PPAR, PXR, RAR, TR, and VDR) SHR (steroid hormone receptor) TR (thyroid hormone receptor) The N terminal region determines transactional activity, the mid portion had DNA binding portion, then a hinge portion and the C terminal portion binds the ligand.

Question 23

What is the structure of RORC, a nuclear binding protein?

Answer 23

The structure of a nuclear binding transcription factor RORC is an amino terminal two zinc fingers 1-30,hinge region 97-268 , ligand binding 269-518 .

Question 24

how does endurance exercise increase mitochondria in muscles?

Answer 24

Increased cytosolic calcium concentration from prolonged stimulation activates the unfolded protein response which via activated transcription faactor 6 which stimulates PGC-1a (pirixisome proliferator-activated receptor gamma coactivator 1-alpha) which activates multiple genes making it the master regulator of mitochondrial biogenesis.

Question 25

How does resistance exercise result in muscle hypertrophy?

Answer 25

Repeated exercise against resistance > 80% of 1 repetition maximun results in more muscle fibrils/myocyte, larger crosssectional area, higher percentage of type II fibers,.Muscle production of IGF-1 is increaaed amd corre;ates with degree of hypertrophy.

01 JUL 1999https://doi.org/10.1152/ajpendo.1999.277.1.E135

.

Musculodystrophy in mice (mdx mutation) can be treatted effectively by over expressing IGF-1 in muscle.

Question 26

How does growth hormone affect muscle development? Can it augment muscle hypertrophy.

Answer 26

Growth hormone receptor ihas a cytoplasmic portion that activates JAK2, a non receptor tyrosine kinase.Multiple pathways are activated including synthesis of Igf-1A which provids the major growth stimulus to bones and muscles. hGH treatment can reduce effects of deficiency but does not cause normal muscle to hypertrophy.

Laron syndrome results from mutation of the GHR producing proportional dwarfism.

Question 27

What is the structure of IGF-1 and it’s receptor ?

Answer 27

IGF-1A is a single chain 70 aa protein with 3 intramolecular sulfide bonds very similar to insulin. IGFR binds IGF-1 with higher affinity than the insulin receptor, bur IGF-1 can bind the insulin receptor

Question 28

What is an oncogene?

Answer 28

An oncogene is a mutated gene whose product has the potential to cause cancer usually either by continously stimulating cell division, or by interupting apoptosis.

Question 29

What are receptor tyrosine kinase oncogenes and can their signaling be rewired to kill cancer cells?

Answer 29

EGFR,PDGFR, and VEGFR are plasma membrane bound receptors that begin cell signaling by activating tyrosine kinase, and oncogene mutations result in continuous kinase activity.

RASTAR is a process that Rewires Aberrant Signaling To Affector Release. Two constructed proteins bind to a tyrosine receptor on the oncogenic protein so that protein 1 contains a proteolytic enzyme that releases a toxic factor (eg Bid) from protein 2. Only cells with an active oncogene develop apoptosis.

Chung et al, Science 364, eaat6982 (3 May 2019)