Basic Pharmacology Lecture Notes PDF

Basic Pharmacology Dr. Mamdouh Oraby  2- Kinase-linked pathways ❑ Structure of kinase receptors: ✓ Large family of membrane receptors. ✓These receptors consist of large extracellular ligand- binding domain (N-terminal) & intracellular domain of different function (C-terminal). ❑ Fun...

Basic Pharmacology Dr. Mamdouh Oraby  2- Kinase-linked pathways ❑ Structure of kinase receptors: ✓ Large family of membrane receptors. ✓These receptors consist of large extracellular ligand- binding domain (N-terminal) & intracellular domain of different function (C-terminal). ❑ Functions of tyrosine kinases: ✓Cell division ✓Cell growth & differentiation ✓Inflammation ✓Tissue repair (regeneration) ✓Apoptosis & immune response  Kinase-linked pathways ❑Types of kinase receptors: A. Tyrosine kinase receptors (TKRs): ▪ Intracellular region contains a tyrosine kinase residue ✓Ex: - Epidermal growth factor (EGF receptors) - Insulin receptors B. Serine/threonine kinases receptors: ✓Serine or threonine residue is phosphorylated rather than tyrosine.  Kinase-linked pathways C. Cytokine receptors: ✓ Activated by cytokines ✓Cytokines: proteins that regulate: ▪ Immune & inflammatory response. ▪ Tissue repair and regeneration ✓Intracellular domain: tyrosine kinase that activates various kinases (ex; Janus kinase, Jak). ✓Ex: Interferons & interleukins & TNF-α  Kinase-linked pathways ▪ N.B: Protein phosphorylation by kinases is an important mechanism for activation of various enzymes, ion channels, receptors, involved in cellular processes. ▪ N.B: Protein kinases catalyze the transfer of phosphate group from high energy phosphate- donating molecule (ex; ATP) to a substate (protein). ▪ Dephosphorylation is controlled by phosphatases.  Kinase-linked pathways A.Signal transduction of tyrosine kinase (Ras/MAPKs pathway): 1) Binding of a ligand + kinase R→ dimerization of the receptor 2) Dimerization → autophosphorylation of intracellular tyrosine 3) The phosphorylated tyrosine acts as binding site (acceptor) for SH2 containing proteins (ex; Grb2) Kinase-linked pathways  Signal transduction of TKRs A. Ras/MAPKs pathway: ▪Binding of phosphorylated tyrosine to SH2 proteins such as (e.x; Grb2): ▪ Phosphorylation and activation of Grb2 proteins ▪ Activation of Ras protein (GTPase-protein) ▪(GDP/GTP exchange protein) ▪ Activation of MAPKs by phosphorylation ▪ Activation of “transcriptional factors” that enter the nucleus and bind to DNA for gene transcription Cellular growth  Signal transduction of TKRs ❑Importance tyrosine kinase inhibitors in the treatment of cancer? - Imatinib is an anticancer that inhibits specific tyrosine kinase R involved the pathogenesis of leukemia  Signal transduction of cytokine R B.1. Jak/Stat Pathway Binding of cytokines to cytokine R Dimerization of the receptor & Autophosphorylation Binding to and phosphorylation of cytosolic tyrosine kinase proteins (Jak) Phosphorylated receptor-Jak complex binds to and phosphorylates SH2 domains of transcriptional factors (Stats). Stat proteins migrate to the nucleus to activate gene expression.  Signal transduction of cytokine R N.B: Stat proteins controls synthesis and release of many inflammatory mediators (response of cells to injury or infection by activation of immune response) Signal transduction of cytokine R B.2. Nuclear factor kappa-B (NFκB pathway). ▪ NFκB: a transcriptional factor that is involved in inflammation and cancer. ▪ NFκB is inhibited by a cytosolic inhibitor (IκB) ▪ Phosphorylation of (IκB) by specific protein kinase (IKK = IκB-kinase) causes dissociation & activation of NFκB ▪ NFκB then enters the nucleus to activate various inflammatory genes.  Binding of cytokines to cytokine receptors Activation of IKK & Phosphorylation of IκB Dissociation & activation of NFκB NFκB enters to the nucleus Transcription of growth & inflammatory genes  Signal transduction of cytokine R ▪N.B: Inhibition of NFκB signaling pathway plays an important role for the treatment of various inflammatory & autoimmune & cancer associated diseases.  Other TKRs pathway (PI3K)/ Akt ) Phosphatidylinositol-3-kinase (PI3K)/ Akt pathway. ✓PI3K, a cytosolic tyrosine kinase, is activated both by GPCRs and TKRs. ✓PI3K signaling controls various cellular functions such as: ▪ Cell differentiation & proliferation ▪ Decrease apoptosis ( ↓ cell death) ▪ ↑ Cell survival  Kinase-linked pathways ❑(PI3K)/ Akt pathway ▪ Ligand (growth factor) binding to the receptor (GPCRs or TKRs) ▪ Activation by phosphorylation of PI3K PI3K ▪ PIP2 → PIP3 ▪ PIP3 binds to & phosphorylates Akt protein to form pAkt  Kinase-linked pathways ❑ N.B: PI3K/ pAkt pathway is associated with cancer progression? ❑ Rational drug design uses molecular targets for PI3K/ pAkt pathway to treat various tumors (ex; endometrial cancer)  3- Ligand & Voltage-gated ion channels ❑ Both receptors are transmembrane proteins that control the ions movement through cell membranes. (by opening & closing). ❑ These proteins have water-filled pores that allow the transport of ions.  Types of ion channels i. Ligand ion channels are activated by exogenous (drugs) / endogenous ligands such as: ✓Glutamate & GABA receptors ✓Nicotinic acetyl choline receptors (nAchRs) ii. Voltage-gated ion channels are activated (open) by depolarization of cell membrane → generation of action potential ✓(Ex: Na+ & K+ & Cl- & Ca2+channels). ❑ Gated channels initiate fast neurotransmission (binding of ligand and opening of the channel occurs in millisecond).  Types of ion channels N.B: No intermediate biochemical steps are involved in the transduction process Ligand & Voltage-gated ion channels ❑Ion channels can be activated by: 1. Binding of ligand with the channel protein (ligand ion channel): 2. Indirect activation by GPCRs (voltage ion channels). 3. Indirect control by intracellular mediators(voltage ion channels). Intracellular Ca+2 Nucleotides such as ATP & GTP  Direct activation of ion channels (ligand- gated channels) ▪ EX 1: Binding of barbiturates with GABAA R on neuronal cell membranes Opening of Cl- channel ions Hyperpolarization of the neuron Inhibition of neuronal transmission (sedation & anesthesia)  Direct activation of ion channels (ligand- gated channels) ▪ EX 2: Binding of Acetyl choline to nicotinic (nAchRs) Rs at neuromuscular junction. ▪ Opening of Na+ channels ▪ Depolarization of muscle cell ▪ Ca +2 release from SR ▪ Muscle contraction  Indirect activation of voltage ion channels 2- Indirect activation GPCRs: ▪ Binding of a ligand to GPCRs ▪ Production of second messenger signaling (cAMP / DAG / IP3) ▪ Activation of protein kinases PKA / PKC ▪ Phosphorylation of intracellular domain of voltage ion channels ▪ Opening or inhibiting the ion channel ▪ Ex1: ß-adrenoceptor agonists in affects voltage Ca+2 channels ▪ Ex2: mAch R (Opening of K+ & closing of Ca+2 channels) Indirect activation of voltage ion channels  Indirect activation of voltage ion channels 3- Indirect control by intracellular mediators or signals: ▪ Ex 1: Intracellular Ca+2 ✓ ↑ intracellular Ca+2 → opening of K+ and Cl- channels ▪ Ex 2: Nucleotides such as ATP & GTP ✓ ATP-Dependent K+ channels: ↑ intracellular ATP closes K+ channels → ↓ K+ outflux → depolarization of the cell & Ca+2 release. Ex; Sulfonylurea & meglitinides closes ATP-K+ channels in the pancreas (↓ K+ outflux & ↑ Ca+2 influx)→ insulin release  4- Signal transduction of Nuclear (DNA) receptors ❑These are receptors for lipid soluble drugs & hormones & vitamins and lipids. ✓Ex: Steroid hormones receptors (Glucocorticoids & Estrogens). ❑Structure of Nuclear receptors: ✓ C-terminal: binds to the ligand ✓ DNA-Binding domain (Zinc fingers): binds to a site on DNA. ✓ N-terminal: binds to other transcriptional factors (proteins).  4- Signal transduction of Nuclear (DNA) receptors ❑ Classification of nuclear receptors: a. Class I ✓The receptors are found in the cytoplasm ✓Ligand binds to nuclear receptors (in cytoplasm) → receptor-ligand complex ✓The complex then translocate to the nucleus → binding to specific site on DNA → transcription of various genes. ✓ Ex: Steroid receptors  Signal transduction of Nuclear (DNA) receptors b. Class II ▪ The receptors are found in the nucleus. ▪ Receptor-ligand complex binds to specific DNA binding site. ✓Ex1: Peroxisome proliferator-activated receptor (PPAR): receptors for drugs (ex; Rosiglitazone & Pioglitazone). ✓Ex2: Thyroid hormone receptors ✓Ex3: Retinoid X receptors (receptor for vit. A)  Receptor associated diseases ❑Various diseases are directly linked to receptor malformation: I. Antibodies )Abs( directed against receptors: ▪ Ex 1: Myasthenia gravis: ✓Autoimmune disease in which Abs inhibit (antagonist) nAchRs → neuromuscular disease. ▪ Ex 2: Graves’ disease: ✓Autoimmune disease in which Abs activates (agonist) thyrotropin R → hyperthyroidism.  Receptor associated diseases II. Mutations in genes encoding receptors: ✓ Mutations in ligand-gated ion channels (GABAA & nicotinic R) can cause epilepsy. ✓ Mutations in GPCRs can cause many diseases & resistance. ✓ Mutation of the growth factor receptors (kinases receptors) is associated with the development of many cancers. ❑https://www.youtube.com/watch?v=Pa11Jw0JAdk&list=PPSV ❑https://www.youtube.com/watch?v=-osiUGKsu7o&list=PPSV ❑https://www.youtube.com/watch?v=N7o0Fkz9iGE ❑https://www.youtube.com/watch?v=VPJG_hy72m8 ❑https://www.youtube.com/watch?v=ewgLd9N3s-4 ❑https://www.youtube.com/watch?v=oa6rvUJlg7o ❑https://www.youtube.com/watch?v=oxX2fq2DBBo 1.Stimulus starts the rapid change in voltage or action potential. sufficient current (stimulus) is required to raise the voltage above the threshold voltage to start membrane depolarization. 2. Depolarization is caused by a rapid rise in membrane potential opening of Na+ channels in the cellular membrane, resulting in a large influx of Na+ ions. 3. Membrane Repolarization results from Na+ channel inactivation and a large efflux of K+ ions resulting from activated K+ channels. 4. Hyperpolarization is a lowered membrane potential caused by the efflux of K+ ions and closing of the K+ channels. 5. Resting state is when membrane potential returns to the resting voltage that occurred before the stimulus occurred.