Cellular CommunicationChapter 11

Local communicationIn what ways do cells communicate locally?In what ways do cells communicate over longer distances?

Regulation by chemical messengersaxonendocrine glandreceptor proteinstarget cellNeurotransmitters released by neuronsHormones release by endocrine glandsreceptor proteinshormone carried by bloodneurotransmitterLock & Key system

Three Stages of Cell SignalingReception1EXTRACELLULARFLUIDReceptorSignalingmoleculePlasma membraneCYTOPLASM1

Fig. 11-6-2Reception1EXTRACELLULARFLUIDReceptorSignalingmoleculePlasma membraneCYTOPLASM1Relay molecules in a signal transduction pathwayTransduction2

Fig. 11-6-3EXTRACELLULARFLUIDPlasma membraneCYTOPLASMReceptorSignalingmoleculeRelay molecules in a signal transduction pathwayActivationof cellularresponseReceptionTransductionResponse123

Steroid Hormones:Hormone(testosterone)ReceptorproteinPlasmamembraneEXTRACELLULARFLUIDDNANUCLEUSCYTOPLASMWhat type of Molecule is a steroid?

ReceptorproteinHormone(testosterone)EXTRACELLULARFLUIDPlasmamembraneHormone-receptorcomplexDNANUCLEUSCYTOPLASM

Hormone(testosterone)EXTRACELLULARFLUIDReceptorproteinPlasmamembraneHormone-receptorcomplexDNANUCLEUSCYTOPLASM

Hormone(testosterone)EXTRACELLULARFLUIDPlasmamembraneReceptorproteinHormone-receptorcomplexDNAmRNANUCLEUSCYTOPLASM

Hormone(testosterone)EXTRACELLULARFLUIDReceptorproteinPlasmamembraneHormone-receptorcomplexDNAmRNANUCLEUSNew proteinCYTOPLASM

Peptide HormonesNuerotransmittersHow will the structure of these molecules cause them to target a cell differently?

Action of protein hormonesactivatesenzymeactivatesenzymeactivates enzymeATPproduces an actionP123cytoplasmreceptor proteinresponsereceptionsecondarymessenger systemsignal-transduction pathwayacts as 2 messengertarget cellplasma membranebinds to receptor proteinprotein hormoneATPactivates cytoplasmic signalcAMPGTPactivatesG-proteintransduction

Ex: Action of epinephrine (adrenaline)activatesprotein kinase-Aactivatesglycogen phosphorylaseactivates adenylyl cyclaseepinephrineliver cellreleased to blood125receptorproteinin cell membranecytoplasm6glycogenactivatesphosphorylase kinaseGTPcAMP4activates G proteinATPglucoseactivates GTP3signaltransductionresponse7GDP

Ion Channel ReceptorsSignalingmolecule(ligand)GateclosedIonsLigand-gatedion channel receptorPlasmamembraneGate openCellularresponseGate closed321Seen with neurotransmitters

Transduction

Signaling moleculeReceptorActivated relaymoleculeInactiveprotein kinase1Activeproteinkinase1Inactiveprotein kinase2ATPADPActiveproteinkinase2PPPPInactiveprotein kinase3ATPADPActiveproteinkinase3PPPPiATPADPPActiveproteinPPPiInactiveproteinCellularresponsePhosphorylation cascadei

Second Messengers

Fig. 11-11First messengerG proteinAdenylylcyclaseGTPATPcAMPSecondmessengerProteinkinase AG protein-coupledreceptorCellular responses

Benefits of a 2 messenger systemAmplification!signalreceptor proteinActivated adenylyl cyclaseamplificationamplificationamplificationamplificationGTPG proteinproductenzymeprotein kinasecAMPNot yetactivated1243567FAST response!amplificationCascade multiplier!

Cellular Response

EXTRA-CELLULARFLUIDSignaling molecule(first messenger)G proteinGTPG protein-coupledreceptorPhospholipase CPIP2IP3DAG(second messenger)IP3-gatedcalcium channelEndoplasmicreticulum (ER)Ca2+CYTOSOL

G proteinEXTRA-CELLULARFLUIDSignaling molecule(first messenger)G protein-coupledreceptorPhospholipase CPIP2DAGIP3(second messenger)IP3-gatedcalcium channelEndoplasmicreticulum (ER)Ca2+CYTOSOLCa2+(secondmessenger)GTP

FigG proteinEXTRA-CELLULARFLUIDSignaling molecule(first messenger)G protein-coupledreceptorPhospholipase CPIP2DAGIP3(second messenger)IP3-gatedcalcium channelEndoplasmicreticulum (ER)Ca2+CYTOSOLVariousproteinsactivatedCellularresponsesCa2+(secondmessenger)GTP

Fig. 11-14Growth factorReceptorPhosphorylationcascadeReceptionTransductionActivetranscriptionfactorResponsePInactivetranscriptionfactorCYTOPLASMDNANUCLEUSmRNAGene

Fig. 11-15ReceptionTransductionResponseBinding of epinephrine to G protein-coupled receptor (1 molecule)Inactive G proteinActive G protein (102 molecules)Inactive adenylyl cyclaseActive adenylyl cyclase (102)ATPCyclic AMP (104)Inactive protein kinase AActive protein kinase A (104)Inactive phosphorylase kinaseActive phosphorylase kinase (105)Inactive glycogen phosphorylaseActive glycogen phosphorylase (106)GlycogenGlucose-1-phosphate(108 molecules)

Homology in hormonesprolactinWhat does this tell you about these hormones?gene duplication?How could these hormones have different effects?

How can 1 signal molecule have multiple responses?

Lets go to the Video!

ApoptosisCell signaling example

Fig. 11-192 m

Fig. 11-20aCed-9protein (active)inhibits Ced-4activityMitochondrionCed-4Ced-3Receptorfor death-signalingmoleculeInactive proteins(a) No death signal

Fig. 11-20b(b) Death signalDeath-signalingmoleculeCed-9(inactive)CellformsblebsActiveCed-4ActiveCed-3ActivationcascadeOtherproteasesNucleases

Fig. 11-21Interdigital tissue1 mm

**transduction: the action or process of converting something and especially energy or a message into another form***The most remarkable characteristic of prolactin (PRL) is the great diversity of effects it produces in different vertebrate species. For example, prolactin stimulates mammary gland growth and milk synthesis in mammals; regulates fat metabolism and reproduction in birds; delays metamorphosis in amphibians, where it may also function as a larval growth hormone; and regulates salt and water balance in freshwater fishes. This list suggests that prolactin is an ancient hormone whose functions have diversified during the evolution of the various vertebrate groups.

Growth hormone (GH) is so similar structurally to prolactin that scientists hypothesize that the genes directing their production evolved from the same ancestral gene. Gene duplication!