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 Stimulatory Activate some sort of behavior, activity, gene expression etc. Inhibitory Shut off behavior, activity, gene expression etc.

Origin of Cell Signaling Began as way for single celled orgs to “communicate” w/ each other Ex: when it gets crowded bacteria can send signals to shut off reproduction (quorum sensing) Has been conserved throughout evolution

Purpose of Signaling in Multi- Cellular Organisms 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 which allow material to be transported b/t cells.

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

Example of Local Regulation Neurotransmitters (chem messengeres in b/t neurons) Serotonin, dopamine etc. carry signals from one part of brain to others Only affects cells in local area

Example of Long Distance Signaling Hormones Released from endocrine glands and travel through blood Affect many target cells throughout the body

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

Types of Receptors on Plasma Membrane Type 1: G protein-coupled receptor: membrane receptor that works w/ help of a G protein…(how gangsta!) G protein acts as an on/off switch: If GDP is bound to G protein  G protein is inactive

hill.com/sites/ /student_view0/chap ter17/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) Can trigger multiple signal pathways at once Types of Receptors on Plasma Membrane

Type 3: Ligand- gated ion channel receptor acts as a gate when receptor changes shape Types of Receptors on Plasma Membrane

Intracellular Receptors Some receptor proteins are found in cytosol/nucleus of target cells Small/hydrophobic chemical messengers can readily cross membrane and activate receptors Ex: hormones! hill.com/sites/ /student_view0/chapter17/animation__intracellular_receptor_m odel.html

Fig Hormone (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID DNA NUCLEUS CYTOPLASM

Fig Receptor protein Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM

Fig Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM

Fig Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormone- receptor complex DNA mRNA NUCLEUS CYTOPLASM

Fig Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA NUCLEUS New protein CYTOPLASM

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

Protein Phosphorylation and Dephosphorylation Signal passed by a cascade of protein phosphorylations Protein kinases transfer PO 4 ’s from ATP to protein (phosphorylation) Protein phosphatases remove PO 4 ’s from proteins (dephosphorylation)

Fig Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 ATP ADP Active protein kinase 2 P P PP Inactive protein kinase 3 ATP ADP Active protein kinase 3 P P PP i ATP ADP P Active protein PP P i Inactive protein Cellular response Phosphorylation cascade i

Second Messengers 1 st messenger: bound onto cell membrane 2 nd messengers: small, nonprotein, water-soluble molecules that spread t/out a cell by diffusion Exs: Cyclic AMP and Ca+2 ions

Cyclic AMP Cyclic AMP (cAMP): most widely used 2 nd messenger Adenylyl cyclase: enzyme in plasma membrane, converts ATP to cAMP in response to an extracellular signal hill.com/sites/ /student_view0/chap ter17/animation__second_messenger__camp.ht ml

Adenylyl cyclase Fig Pyrophosphate P P i ATP cAMP Phosphodiesterase AMP

First messenger Fig G protein Adenylyl cyclase GTP ATP cAMP Second messenger Protein kinase A G protein-coupled receptor Cellular responses

Step 3: Response AKA: “output response” Usually activates transcription to make a protein or to regulate enzyme activity.

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