Cell Communication John Girard Project Opening Doors

Cell Communication Cells communicate by chemical “messengers” Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells In local signaling, animal cells and unicellular organisms may communicate by direct contact, called cell-cell recognition

Cell Communication Animal cells communicate using local regulators, messenger molecules that travel only short distances In long-distance signaling, plants and animals use chemicals called hormones

Local and Long-Distance Cell Communication in Animals

Local and Long-Distance Cell Communication in Animals

Local and Long-Distance Cell Communication in Animals

Communication by Direct Contact between Cells

Communication by Direct Contact between Cells

Cell Communication A signal transduction pathway is a series of steps by which a signal on a cell’s surface is converted into a specific cellular response Cells receiving signals go through three processes: Reception Transduction Response

Overview of Cell Signaling

Overview of Cell Signaling

Overview of Cell Signaling

Receptors in the Plasma Membrane There are three main types of membrane receptors: G protein-coupled receptors Tyrosine kinase receptors Ion channel receptor

The Structure of a G-Protein-coupled Receptor

The Functioning of a G-Protein-coupled Receptor

The Functioning of a G-Protein-coupled Receptor

The Functioning of a G-Protein-coupled Receptor These biochemical pathways include developmental pathways, sensory perception in vision and smell. Bacteria that often cause disease by secreting toxins. These toxins may interfere with G-protein functions. 60% of all medicines exert their effect by influencing G-protein pathways.

The Functioning of a G-Protein-coupled Receptor Activity: Pathways with Friends Instructions Form groups of 6 people each Create space for your group to interact without bumping into each other Rules: Each person in the group will get a card Do not let others in your group know what your card says When prompted, follow the instructions on the card

The Functioning of a G-Protein-coupled Receptor Activity: Pathways with Friends

The Functioning of a G-Protein-coupled Receptor Activity: Pathways with Friends

The Functioning of a G-Protein-Coupled Receptor Activity:

The Functioning of a G-Protein-Coupled Receptor Activity:

Receptors in the Plasma Membrane Tyrosine-kinase receptors are membrane receptors that attach phosphates to tyrosines A tyrosine-kinase receptor can trigger multiple signal transduction pathways at once A major class of membrane proteins having enzymatic activity A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

The Structure and Function of a Tyrosine-Kinase Receptor

The Structure and Function of a Tyrosine-Kinase Receptor When activated, tyrosine-kinase receptors can activate more than one signal-transduction pathway at one time. This is important when an event like cell reproduction requires a number of biochemical pathways to be activated at once.

The Structure and Function of a Tyrosine-Kinase Receptor Activity:

The Structure and Function of a Tyrosine-Kinase Receptor Activity:

A Ligand-Gated Ion-Channel Receptor

A Ligand-Gated Ion-Channel Receptor

A Ligand-Gated Ion-Channel Receptor

Steroid Hormone Interacting with an Intracellular Receptor (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID DNA NUCLEUS CYTOPLASM Steroid Hormone Interacting with an Intracellular Receptor Signal must be lipid soluble to make into the cytosol. These signals are usually steroid hormones, thyroxine, and nitric oxide. Testosterone enters the cell and binds with a receptor protein found in the cytoplasm. This complex now moves to the nucleus where is acts a transcription factor and helps transcribes certain genes.

Steroid Hormone Interacting with an Intracellular Receptor protein Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM Steroid Hormone Interacting with an Intracellular Receptor Signal must be lipid soluble to make into the cytosol. These signals are usually steroid hormones, thyroxine, and nitric oxide. Testosterone enters the cell and binds with a receptor protein found in the cytoplasm. This complex now moves to the nucleus where is acts a transcription factor and helps transcribes certain genes.

Steroid Hormone Interacting with an Intracellular Receptor (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA NUCLEUS CYTOPLASM Steroid Hormone Interacting with an Intracellular Receptor Signal must be lipid soluble to make into the cytosol. These signals are usually steroid hormones, thyroxine, and nitric oxide. Testosterone enters the cell and binds with a receptor protein found in the cytoplasm. This complex now moves to the nucleus where is acts a transcription factor and helps transcribes certain genes.

Responses to Other Signals Inner chamber Outer –90 mV 140 mM 5 mM KCI K+ Cl– Potassium channel (a) Membrane selectively permeable to K+ (b) Membrane selectively permeable to Na+ +62 mV 15 mM NaCI 150 mM Na+ Sodium

Responses to Other Signals CYTOPLASM Reception Plasma membrane Cell wall Phytochrome activated by light Light Transduction Second messenger produced cGMP NUCLEUS 1 2 Specific protein kinase 1

Responses to Other Signals CYTOPLASM Reception Plasma membrane Cell wall Phytochrome activated by light Light Transduction Second messenger produced cGMP Specific protein kinase 1 NUCLEUS 1 2 kinase 2 Ca2+ channel opened Ca2+

Responses to Other Signals CYTOPLASM Reception Plasma membrane Cell wall Phytochrome activated by light Light Transduction Second messenger produced cGMP Specific protein kinase 1 NUCLEUS 1 2 kinase 2 Ca2+ channel opened Ca2+ Response 3 Transcription factor 1 factor 2 Translation De-etiolation (greening) response proteins P

Signal Transduction Pathways Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation A major class of membrane proteins having enzymatic activity A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

Signal Transduction Pathways Protein phosphatases remove the phosphates from proteins, a process called dephosphorylation This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off A major class of membrane proteins having enzymatic activity A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

A Phosphorylation Cascade Signaling molecule Receptor Activated relay molecule Serine and threonine of the two amino acids that receive the phosphate group on the receiving protein. Approximately 1% of all our genes code for various protein kinases.

A Phosphorylation Cascade Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase

A Phosphorylation Cascade Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 2 ATP ADP P PP i Protein kinases are proteins that transfer phosphate groups from ATP to another protein. Serine and threonine of the two amino acids that receive the phosphate group on the receiving protein. Approximately 1% of all our genes code for various protein kinases. Protein phosphatases remove a phosphate group from proteins and can deactivate a protein kinase.

A Phosphorylation Cascade Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 2 ATP ADP P PP 3 i

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

Second Messengers The extracellular signal molecule that binds to the receptor is a pathway’s first messenger Second messengers are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion A major class of membrane proteins having enzymatic activity A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

Second Messengers Cyclic AMP (cAMP) is one of the most widely used second messengers Adenylyl cyclase, an enzyme in the plasma membrane, converts ATP to cAMP in response to an extracellular signal A major class of membrane proteins having enzymatic activity A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

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

Epinephrine Transduction Pathway cAMP Second messenger Adenylyl cyclase G protein-coupled receptor ATP GTP G protein Epinephrine

Epinephrine Transduction Pathway cAMP Second messenger Adenylyl cyclase G protein-coupled receptor ATP GTP G protein Epinephrine Inhibition of glycogen synthesis Promotion of glycogen breakdown Protein kinase A

cAMP as a Second Messenger Activity:

cAMP as a Second Messenger Activity:

Calcium Ions Calcium ions (Ca2+) act as a second messenger in many pathways Calcium is an important second messenger because cells can regulate its concentration A major class of membrane proteins having enzymatic activity A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

The Maintenance of Calcium Ion Concentrations in an Animal Cell High Ca++ Low Ca++ Some signal molecules in animals induce responses by increasing the amount of Ca++ in the cytosol This is used in muscle and nerve cells

Inositol Triphosphate Pathways leading to the release of calcium involve inositol triphosphate (IP3) and diacylglycerol (DAG) as additional second messengers

Calcium and Inositol Triphosphate in Signaling Pathways EXTRA- CELLULAR FLUID G protein GTP Phospholipase C PIP2 DAG Endoplasmic reticulum (ER) Ca2+ CYTOSOL Signaling molecule (first messenger) IP3 IP3-gated calcium channel (second messenger) G protein-coupled receptor

Calcium and Inositol Triphosphate in Signaling Pathways G protein PIP2 EXTRA- CELLULAR FLUID Signaling molecule (first messenger) GTP IP3 DAG IP3-gated calcium channel Endoplasmic reticulum (ER) Ca2+ CYTOSOL Phospholipase C (second messenger) (second messenger) G protein-coupled receptor DAG = diacylglycerol IP3 = inositol triphosphate

Calcium and Inositol Triphosphate in Signaling Pathways DAG Various proteins activated Cellular responses Ca2+ (second messenger) Endoplasmic reticulum (ER) CYTOSOL IP3-gated calcium channel PIP2 IP3 (second messenger) GTP G protein G protein-coupled receptor EXTRA- CELLULAR FLUID Signaling molecule (first messenger) Phospholipase C DAG = diacylglycerol IP3 = inositol triphosphate

Growth factor Receptor Phosphorylation cascade Reception Transduction Active transcription factor Response P Inactive CYTOPLASM DNA NUCLEUS mRNA Gene Nuclear Response to a Signal: The Activation of a Specific Gene by a Growth Factor

Signal Amplification: Stimulation of Glycogen Breakdown by Epinephrine

Is Signal Transduction Important? Androgen Insensitivity Syndrome: Genetic male (XY) without androgen receptors The gene for the syndrome is on the X chromosome in band Xq11-q12. The gene codes for the androgen receptor. Result: No signal transduction!

Cell Communication Free-Response Questions 1992 2. Biological recognition is important in many processes at the molecular, cellular, tissue, and organismal levels. Select three of the following, and for each of the three that you have chosen, explain how the process of recognition occurs and give an example. Organisms recognize others as members of their own species. Neurotransmitters are recognized in the synapse. Antigens trigger antibody responses. Nucleic acids are complementary. Target cells respond to specific hormone

Cell Communication Free-Response Questions 1999 2. Communication occurs among the cells in a multicellular organism. Choose THREE of the following examples of cell-to-cell communication, and for each example, describe the communication that occurs and the types of responses that result from this communication. Communication between two plant cells Communication between two immune-system cells Communication either between a neuron and another neuron, or between a neuron and a muscle cell Communication between a specific endocrine-gland cell and its target cell

Cell Communication Free-Response Questions 2007 1. Membranes are essential components of all cells. Identify THREE macromolecules that are components of the plasma membrane in a eukaryotic cell and discuss the structure and function of each. Explain how membranes participate in THREE of the following biological processes: Muscle contraction Fertilization of an egg Chemiosmotic production of ATP Intercellular signaling

Cell Communication Free-Response Questions 2008 1. The physical structure of a protein often reflects and affects its function. Describe THREE types of chemical bonds/interactions found in proteins. For each type, describe its role in determining protein structure. Discuss how the structure of a protein affects the function of TWO of the following. Muscle contraction Regulation of enzyme activity Cell signaling Abnormal hemoglobin is the identifying characteristic of sickle cell anemia. Explain the genetic basis of the abnormal hemoglobin. Explain why the sickle cell allele is selected for in certain areas of the world.