Chapter 11 Cell Communication

LE 11-2 Exchange of mating factors Mating Receptor a   factor a  a factor Yeast cell, mating type a Yeast cell, mating type  a/  New a/  cell

Signal Transduction Pathways Local signaling Local signaling Cell junctions Cell junctions Cell-cell recognition Cell-cell recognition Local regulators – growth factors Local regulators – growth factors Paracrine signaling Paracrine signaling Synaptic signaling Synaptic signaling Long-Distance signaling Long-Distance signaling Endocrine signaling - hormones Endocrine signaling - hormones

LE 11-3a Plasma membranes Gap junctions between animal cells Cell junctions Plasmodesmata between plant cells

LE 11-3b Cell-cell recognition

LE 11-4a Paracrine signaling Local regulator diffuses through extracellular fluid Secretory vesicle Secreting cell Target cell Local signaling Electrical signal along nerve cell triggers release of neurotransmitter Neurotransmitter diffuses across synapse Synaptic signaling Target cell is stimulated

LE 11-4b Endocrine cell Blood vessel Long-distance signaling Hormone travels in bloodstream to target cells Hormonal signaling Target cell

Three Stages Reception Reception Transduction Transduction Response Response

LE 11-5_1 EXTRACELLULAR FLUID Reception Plasma membrane Transduction CYTOPLASM Receptor Signal molecule

LE 11-5_2 EXTRACELLULAR FLUID Reception Plasma membrane Transduction CYTOPLASM Receptor Signal molecule Relay molecules in a signal transduction pathway

LE 11-5_3 EXTRACELLULAR FLUID Reception Plasma membrane Transduction CYTOPLASM Receptor Signal molecule Relay molecules in a signal transduction pathway Response Activation of cellular response

Reception Receptor-Ligand interaction Receptor-Ligand interaction Receptors Receptors Intracellular – testosterone Intracellular – testosterone In plasma membrane – Figure 11.7 In plasma membrane – Figure 11.7 G-protein linked receptor G-protein linked receptor Receptor tyrosine kinases Receptor tyrosine kinases Ion channel receptors – ligand-gated ion channel Ion channel receptors – ligand-gated ion channel

LE 11-6 EXTRACELLULAR FLUID Plasma membrane The steroid hormone testosterone passes through the plasma membrane. Testosterone binds to a receptor protein in the cytoplasm, activating it. The hormone- receptor complex enters the nucleus and binds to specific genes. The bound protein stimulates the transcription of the gene into mRNA. The mRNA is translated into a specific protein. CYTOPLASM NUCLEUS DNA Hormone (testosterone) Receptor protein Hormone- receptor complex mRNA New protein

LE 11-7aa Segment that interacts with G proteins Signal-binding site G-protein-linked receptor

LE 11-7ab G-protein-linked receptor GDP CYTOPLASM Plasma membrane G protein (inactive) Enzyme GDP GTP Activated receptor GTP Signal molecule Inactive enzyme Activated enzyme Cellular response P i

LE 11-7b Signal molecule  Helix in the membrane Signal-binding site Tyr Tyrosines Receptor tyrosine kinase proteins (inactive monomers) CYTOPLASM Tyr Activated tyrosine- kinase regions (unphosphorylated dimer) Signal molecule Dimer Fully activated receptor tyrosine-kinase (phosphorylated dimer) Tyr P P P P P P ATP 6 ADP Tyr P P P P P P Inactive relay proteins Cellular response 2 Cellular response 1 Activated relay proteins 6

LE 11-7c Signal molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate closed Gate open Cellular response

Transduction Cascades of molecular interactions Cascades of molecular interactions Signal transduction pathway Signal transduction pathway Protein phosphorylation and dephosphorylation Protein phosphorylation and dephosphorylation Second messengers Second messengers Calcium ions and IP 3 Calcium ions and IP 3

LE 11-8 Signal molecule Activated relay molecule Receptor Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 Active protein kinase 2 Inactive protein kinase 3 Active protein kinase 3 ADP Inactive protein Active protein Cellular response Phosphorylation cascade ATP PP P i ADP ATP PP P i ADP ATP PP P i P P P

LE 11-9 ATPCyclic AMPAMP Adenylyl cyclase Pyrophosphate PP i Phosphodiesterase H2OH2O

LE cAMP ATP Second messenger First messenger (signal molecule such as epinephrine) G-protein-linked receptor G protein Adenylyl cyclase Protein kinase A Cellular responses GTP

LE ATP EXTRACELLULAR FLUID ATP Mitochondrion Ca 2+ pump Plasma membrane CYTOSOL Endoplasmic reticulum (ER) Ca 2+ pump Ca 2+ pump High [Ca 2+ ] Key Nucleus Low [Ca 2+ ]

LE 11-12_1 CYTOSOL Ca 2+ Endoplasmic reticulum (ER) IP 3 -gated calcium channel IP 3 (second messenger) DAG PIP 2 G-protein-linked receptor Phospholipase C G protein Signal molecule (first messenger) EXTRACELLULAR FLUID GTP

LE 11-12_2 CYTOSOL Ca 2+ Endoplasmic reticulum (ER) IP 3 -gated calcium channel IP 3 (second messenger) DAG PIP 2 G-protein-linked receptor Phospholipase C G protein Signal molecule (first messenger) EXTRACELLULAR FLUID GTP Ca 2+ (second messenger)

LE 11-12_3 CYTOSOL Ca 2+ Endoplasmic reticulum (ER) IP 3 -gated calcium channel IP 3 (second messenger) DAG PIP 2 G-protein-linked receptor Phospholipase C G protein Signal molecule (first messenger) EXTRACELLULAR FLUID GTP Ca 2+ (second messenger) Various proteins activated Cellular re- sponses

The Response Cytoplasmic and nuclear responses Cytoplasmic and nuclear responses Fine tuning Fine tuning Signal amplification Signal amplification Specificity Specificity Efficiency Efficiency Termination Termination

LE Binding of epinephrine to G-protein-linked receptor (1 molecule) Reception Transduction Inactive G protein Active G protein (10 2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10 2 ) ATP Cyclic AMP (10 4 ) Inactive protein kinase A Inactive phosphorylase kinase Active protein kinase A (10 4 ) Active phosphorylase kinase (10 5 ) Active glycogen phosphorylase (10 6 ) Inactive glycogen phosphorylase Glycogen Response Glucose-1-phosphate (10 8 molecules)

LE Reception Growth factor Receptor Phosphorylation cascade Transduction CYTOPLASM Inactive transcription factor Active transcription factor P Response Gene mRNA DNA NUCLEUS

LE Signal molecule Receptor Relay molecules Response 1 Response 2Response 3 Cell B. Pathway branches, leading to two responses Cell A. Pathway leads to a single response Cell C. Cross-talk occurs between two pathways Response 4 Response 5 Activation or inhibition Cell D. Different receptor leads to a different response

LE Signal molecule Plasma membrane Receptor Scaffolding protein Three different protein kinases