Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 1 One Biologist’s Perspective Drena Dobbs BCB & GDCB Iowa State University Signal Transduction

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 2 Thanks to : Howard Booth Biology Eastern Michigan University for Slides modified from his lecture Cell-Cell Communication Marit Nilsen-Hamilton BBMB Iowa State University for Slides copied from her lectures Small G proteins GPCRs

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 3 An Aging Biologist’s Perspective Signal Transduction

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 4 The Perspective of A Biologist Signal Transduction Who Studies Aging

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 5 Greer, E. L. et al. J Cell Sci 2008;121:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 6 The Perspective of A Biologist Who Studies G-proteins Signal Transduction

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 7 Buchsbaum, R. J. J Cell Sci 2007;120:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 8 Schwartz, S. L. et al. J Cell Sci 2007;120:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 9 1.Why is Signal Transduction so important? 2.What are Components of Signal Transduction Pathways? Cytokines & Cytokine Receptors (e.g. Ig-superfamily Receptors) Hormones & Hormone Receptors (e.g., GPCRs) G-Proteins Small G-proteins (e.g., Ras, Rab, Rho) Heterotrimeric G-proteins Second Messengers (e.g., Ca ++, cAMP, DAG) Kinases & Phosphatases Transcription Regulatory Factors and Co-factors (RF&CFs) Post-transcriptional RF&CFs Translational RF&CFs Post-translational RF&CFs Metabolic RF&CFs 3.How is Signal Transduction Studied (Experimentally)?

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 10 Watch: Inner Life of a Cell Go to U-Tube!! - or better, HARVARD: html html Leukocytes = White blood cells Function in immunity

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 11 A few URLs: the tip of an iceberg! - p. 1 Kimballs’ Biology Pages - Glossary, Notes, etc: Cell Signaling: l Hormones in Humans:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 12 A few URLs: the tip of an iceberg! - p. 2 Cytokines & Cytokine Receptors: ml#Cytokine_Receptors ml#Cytokine_Receptors GPCRs: g.html#GPCRs g.html#GPCRs G-proteins: p53: ATPases:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 13 Endocrinology = re: Hormones 3 basic types of chemical signaling: Endocrine - cell secretes “chemicals” that are carried by blood or tissue fluids to distant cells upon which they act Ex: Release of Hormones (which can be proteins, peptides, steroids) Paracrine - cell releases “chemical” signals that diffuse and interact with receptors on nearby cells Ex: Release of Cytokines that cause an inflammatory response Release of Neurotransmitters at synapses in the nervous system Autocrine - cell signals itself with a chemical that it both synthesizes and responds to Autocrine signaling can occur: Solely within the cytoplasm of the cell By secreted chemical interacting with receptors on surface of same cell

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 14 Cytokines What are cytokines? Cell signaling molecules secreted by a cell, which: signal other cells in a paracrine fashion or signal the secreting cell (in an autocrine fashion) Play important roles in immunity Structurally diverse; mainly small 8-30 kDa, water-soluble proteins & glycoproteins Ex: various lymphokines, chemokines, interleukins What are other types of cell signaling molecules? Hormones, Growth Factors, Neurotransmitters

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 15 Cytokine Receptors Dozens of cytokine receptors have been discovered Most fall into one of several major families: 1.Receptor Tyrosine Kinases (RTKs) 2.TNF (tumor necrosis factor) superfamily receptors 3.TGF-  (transforming growth factor) receptors (Ser/Thr Kinases) 4.Immunoglobulin superfamily receptors (IgRs) 5.Chemokine receptors (e.g., GPCRs) 6.Type I/II cytokine receptors that trigger JAK-STAT pathways JAK-STAT signaling mediates cellular responses to cytokines and growth factors. Employing Janus kinases (JAKs) and Signal Transducers & Activators of Transcription (STATs), the pathway transduces the signal carried by these extracellular polypeptides to the cell nucleus, where activated STAT proteins modify gene expression cytokinesgrowth factors Janus kinasesSignal Transducers & Activators of Transcriptionextracellularpolypeptidescell nucleus STAT proteins

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 16 Review a few topics: How cells communicate Electrical and chemical signals Receptor types and how they function Local regulation of cells

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 17 Chemical Autocrine & Paracrine: local signaling via cytokines. neurotransmitters Endocrine: distant targets via hormones Electrical Nervous system: fast, specific, distant target Gap junctions: local Types of Cell to Cell Communication:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 18 Gap Junctions and CAMs Protein channels - connexins Direct flow to neighbor Electrical - ions (charge) Chemicals/proteins CAMs - Cell Adhesion Molecules Need direct surface contact Chemicals/proteins Figure 6-1a, b: Direct and local cell-to-cell communication Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 19 Paracrine & Autocrine Signaling Local communication Signals diffuse to targets Ex: Cytokines Autocrine– receptor on same cell Paracrine – neighboring cells Figure 6-1c: Direct and local cell-to-cell communication Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 20 Made in endocrine cells Transported via blood Receptors on target cells Long Distance Communication: Endocrine Signaling - via Hormones Figure 6-2a: Long distance cell-to-cell communication Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 21 Neurons Electrical signal travels down axon (can be very long!!) Change in potential causes release (in synapse) of neurotransmitters that bind to receptors on nearby target cell Neurohormones Hormones transported via blood to target A neurohormone is any hormone produced by neurosecretory cells, usually in the brain. Neurohormonal activity is distinguished from that of classical neurotransmitters as it can have effects on cells distant from the source of the hormone. Examples?hormoneneurosecretorycellsbrain neurotransmitters GnRH = Gonadotropin releasing hormone CRH = Corticotropin releasing hormone TRH = Thyrotropin-releasing hormone Dopamine Prolactin inhibiting hormone Orexin (aka hypocretin) Long Distance Communication: Neurons and Neurohormones

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 22 Long Distance Communication: Neurons and Neurohormones Figure 6-2b, c: Long distance cell-to-cell communication Figure 6-2 b: Long distance cell-to-cell communication Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 23 Summary: Components of Signaling Pathways Extracellular signaling molecule (cytokine, hormone) Receptor Intracellular signaling molecule (kinase, second messenger) Target protein (kinase, transcription factor) Response Figure 6-3: Signal pathways Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 24 Receptor locations? Intracellular: Cytosolic or Nuclear Lipophilic ligand enters cell Often activates transcription of gene(s) Relatively slow response Cell surface: Transmembrane Lipophobic ligand can't enter cell Often activates protein kinase cascade Relatively fast response Figure 6-4: Target cell receptors Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 25 Integrins (in Inner Life of Cell) Ligand-gated channels Receptor enzymes RTKs & other “single pass” transmembrane (TM) domain receptors G-protein coupled GPCRs & other 7 TM domain receptors) Membrane Receptor Classes

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 26 Membrane Receptor Classes Figure 6-5: Four classes of membrane receptors Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 27 Receptor Enzyme: ReceptorTyrosine Kinase Transmembrane (TM) proteins Transduce signal across membrane Binding of ligand to extracellular receptor domain Somehow transduces signal through TM domain Resulting in activation of intracellular kinase domain Figure 6-10: Tyrosine kinase, an example of a receptor-enzyme Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 28 G Protein-Coupled Receptors = GPCRs Figure 6-11: The G protein-coupled adenylyl cyclase-cAMP system Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 29 G Protein-Coupled Receptors Hundreds of types Main signal transducers in eukaryotic cells Activate enzymes Open ion channels (e.g., to allow influx of Ca ++ ) Amplify signals: Adenyl cyclase >>> cAMP Activate downstream effectors Effector? Protein/enzyme “activated” by another protein But - What is a G-protein???

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 30 Summary: Steps in Signal Transduction Signal = ligand (small molecule) Binds Receptor, which activates: Protein kinases Tyr or Ser/Thr & Second messengers cAMP, Ca ++, DAG, which result in activation of “downstream” proteins or enzymes via: Phosphorylation cascades or other post-translational modifications (PTMs) or Ca ++ binding Resulting in Cellular Response Figure 6-8: Biological signal transduction Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 31 Ca ++ - Mediated Signaling? Figure 6-15: Calcium as an intracellular messenger In neurons: Electrical signal causes: Ca ++ release from intracellular stores (endoplasmic reticulum, ER) or Influx of Ca ++ through voltage-gated Ca ++ channels Activates Ca ++ binding proteins Causing conformational changes that Activate downstream effectors Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 32 Critical Aspect: Signal Amplification Small signal produces large cellular response via amplification enzymes Ex: “phosphorylation” or “kinase” cascade ( MAP kinase cascade) Figure 6-7: Signal amplification Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 33 Signal Transduction: the Big Picture Copyright © 2004 Pearson Education, Inc., pub as Benjamin Cummings Fig 6-14: Summary of signal transduction systems

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 34 Take home messages: 1.Signal Transduction involves transfer of signal information, often from outside a cell (environmental stimulus) to inside, evoking a response Extracellular Signal >>> Cellular Response 2.Amplification of signal occurs via activation of kinases (“kinase cascades”) or release of Ca ++ (Ca ++ -mediated signaling) 3.In eukaryotic cells, membranes and membranous compartments (nucleus, ER, Golgi apparatus, plasma membrane) play critical roles in signal transduction 4.Cross-talk occurs between components of different signal transduction pathways/networks

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 35 Signal Transduction & Cancer: 1.Cancer is a genetic disease (although only a few rare types of cancer are known to be inherited) 2.Most of what we know about cancer - and about normal development - was built on results of basic biological research on rare cancer-causing viruses 3.Such studies have shown that: All known cancers result from mutations in components of signal transduction networks (& genes that control cell division or DNA repair) Viral oncogenes are variants of “normal” cellular genes that have been “picked up” by viruses

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings for BCB 570 4/8/08 - Drena Dobbs ISU 36 HPV, Vaccines & Cancer 1.Cervical cancer (a deadly cancer in women) is caused by certain strains of Human Papilloma Virus (HPV), for which a vaccine is now available 2.Many health insurance policies do not cover the cost of Gardasil (but do cover the cost of Viagra…) 3.HPV is sexually-transmitted 4.Both men & women can be infected with no obvious symptoms 5.~75% of US reproductive-age population has been infected with one or more types of genital HPV 6.HPV also causes certain cancers in men (~10% as frequent as cervical cancer in women)