Unit 2 – The CellUnit 2 – The Cell

Chapter 11~Chapter 11~Cell Cell

CommunicationCommunication

Signal-transduction Signal-transduction pathwaypathway

DefDef: Signal on a cell’s surface is converted into a : Signal on a cell’s surface is converted into a specific cellular responsespecific cellular response

Local signaling Local signaling (short distance): (short distance): √ Paracrine (growth factors)√ Paracrine (growth factors)

√ Synaptic (neurotransmitters)√ Synaptic (neurotransmitters) Long distanceLong distance: hormones: hormones

Stages of cell signalingStages of cell signaling

Sutherland (‘71)Sutherland (‘71) Glycogen depolymerization by epinephrineGlycogen depolymerization by epinephrine 3 steps:3 steps:

•Reception: target cell detection •Reception: target cell detection •Transduction: single-step or series of changes•Transduction: single-step or series of changes

•Response: triggering of a specific cellular •Response: triggering of a specific cellular responseresponse

Protein phosphorylationProtein phosphorylation

Protein activity regulationProtein activity regulation Adding phosphate from Adding phosphate from

ATP to a protein ATP to a protein (activates proteins)(activates proteins)

Enzyme: protein kinases Enzyme: protein kinases (1% of all our genes) (1% of all our genes)

Example: cell Example: cell reproductionreproduction

Reversal enzyme: Reversal enzyme: protein phosphatasesprotein phosphatases

Second messengersSecond messengers

Non-protein signaling Non-protein signaling pathway (pathway (

Example: cyclic AMP Example: cyclic AMP (cAMP)(cAMP)

Ex: Glycogen Ex: Glycogen breakdown with breakdown with epinephrineepinephrine

Enzyme: adenylyl Enzyme: adenylyl cyclasecyclase

G-protein-linked receptor G-protein-linked receptor in membrane (guanosine in membrane (guanosine di- or tri- phosphate)di- or tri- phosphate)

Cellular responses to Cellular responses to signalssignals

Cytoplasmic Cytoplasmic activity regulationactivity regulation

Cell metabolism Cell metabolism regulationregulation

Nuclear Nuclear transcription transcription regulationregulation