Cell Communication Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes.

Essential Knowledge 3D1: Cell communication processes share common features that reflect evolutionary history. 3D2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. 3D3: Signal transduction pathways link signal reception with cellular response. 3D4: Changes in signal transduction pathways can alter cellular responses.

Simple Communication Turn cell activity on Turn cell activity off Stimulatory Turn cell activity on Inhibitory Turn cell activity off

Origin of Cell Signaling Single celled orgs to “communicate” w/ each other Ex: when it gets crowded bacteria can send signals to shut off reproduction (quorum sensing) Conserved through evolution

Coordinate cellular actions Why Talk? Coordinate cellular actions Ex: when frightened you release epinephrine, which triggers mobilization of glucose and other energy resources Fight or flight

Distance of Communication 1) Direct contact 2) Local communication 3) Long distance

Example of Direct Contact Plant cells walls have plasmodesmata  allow material to be transported b/t cells.

Example of Direct Contact Antigen-presenting White blood cell directly contacts helper T cells Activates immune responses

Example of Local Regulation Neurotransmitters (chem messengeres in b/t neurons) Serotonin, dopamine common nm’s.

Example of Long Distance Signaling Hormones Released from endocrine glands and travel in blood Affect target cells

Highly specific proteins Step 1: Reception Signal molecule (aka ligand) binds to a receptor protein  change shape Highly specific proteins

Type 1 Receptor: G protein G protein acts as an on/off switch: If GDP is bound to G protein  G protein is inactive

http://highered. mcgraw-hill http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors_that_activate_g_proteins.html

G Proteins and Medicine Diabetes, blindness, allergies, depression and some cancers are believed to come from dysfunctional G proteins Up to 60% of medicines used influence G-Protein Pathways

Type 2: Receptor Tyrosine Kinases Membrane receptors that attach phosphates to tyrosines (a.acids) Tyrosine = amino acid!

Type 3: Ligand-gated ion channel Receptor acts as a gate when receptor changes shape

Intracellular Receptors Small/hydrophobic chemical messengers can cross membrane and activate receptors in cytoplasm. Ex: hormones! http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__intracellular_receptor_model.html

Hormone (testosterone) Plasma membrane Receptor protein DNA NUCLEUS Fig. 11-8-1 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein DNA Figure 11.8 Steroid hormone interacting with an intracellular receptor NUCLEUS CYTOPLASM

Hormone (testosterone) Plasma membrane Receptor protein Hormone- Fig. 11-8-2 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.8 Steroid hormone interacting with an intracellular receptor NUCLEUS CYTOPLASM

Hormone (testosterone) Plasma membrane Receptor protein Hormone- Fig. 11-8-3 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.8 Steroid hormone interacting with an intracellular receptor NUCLEUS CYTOPLASM

Hormone (testosterone) Plasma membrane Receptor protein Hormone- Fig. 11-8-4 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.8 Steroid hormone interacting with an intracellular receptor mRNA NUCLEUS CYTOPLASM

Hormone (testosterone) Plasma membrane Receptor protein Hormone- Fig. 11-8-5 Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA Figure 11.8 Steroid hormone interacting with an intracellular receptor mRNA NUCLEUS New protein CYTOPLASM

Relayers are mainly proteins Step 2: Transduction Multiple steps Can amplify a signal! Relayers are mainly proteins Domino effect!

Protein Phosphorylation Signal passed by a protein phosphorylations Protein kinases transfer PO4’s from ATP to protein (phosphorylation)

Phosphorylation cascade Fig. 11-9 Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 ATP Phosphorylation cascade ADP Active protein kinase 2 P PP P i Figure 11.9 A phosphorylation cascade Inactive protein kinase 3 ATP ADP Active protein kinase 3 P PP P i Inactive protein ATP ADP P Active protein Cellular response PP P i

2nd messengers: transfer messages in cytoplasm. Ex: cAMP Second Messengers 1st messenger: ligand 2nd messengers: transfer messages in cytoplasm. Ex: cAMP

Cyclic AMP (cAMP): most widely used 2nd messenger Adenylyl cyclase: enzyme in plasma membrane, converts ATP to cAMP in response to an extracellular signal http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__second_messenger__camp.html

Fig. 11-10 Adenylyl cyclase Phosphodiesterase Pyrophosphate P P ATP cAMP AMP Figure 11.10 Cyclic AMP

First messenger Adenylyl cyclase G protein GTP G protein-coupled Fig. 11-11 First messenger Adenylyl cyclase G protein G protein-coupled receptor GTP ATP Second messenger cAMP Figure 11.11 cAMP as second messenger in a G-protein-signaling pathway Protein kinase A Cellular responses

Step 3: Response AKA: “output response” Usually activates transcription to make a protein. Figure 11.14 Nuclear responses to a signal: the activation of a specific gene by a growth factor

Importance of Cell Signaling Diseases result from incorrect signaling Drugs often target signaling mechanisms Poisons and pesticides often target signaling pathways

Mr. Anderson Cell Signaling