The Three Stages of Cell SignalingBy: Madeline Meyer and Carlos Sanchez

ReceptionTransducti

on Response

Why is this important?• Perceive Surroundings• Tissue Repair• Homeostasis• Functioning Immune System

RECEPTION

G Protein-Coupled Receptors (GPCRs)• Cell-surface transmembrane protein, works with G

protein, which binds GTP to make energy• Signal mol.s = ligands (“link” to another mol. to begin

transduction)• Widespread functions, therefore widespread structures

(all similar)

G Protein-Coupled Receptors

Receptor Tyrosine Kinases (RTK)• Enzymatic activity

• Kinase catalyzes transfer of phosphate groups• Tyrosine kinases catalyze transfer of phosphate group

from ATP to amino acid tyrosine on substrate protein• *ONE tyrosine kinase complex can activate > 10

transduction pathways*• Different from G proteins, which activate only 1 pathway each

Evolutionary significance• All G proteins are similarly shaped (with vital

differences)• This means that the G protein likely evolved very early, hence

it plays a large role in signal transduction in many distant organisms

Transduction

Phosphorylation Cascades• Protein Kinases- Starts off the process • One enzyme phosphorylates another,• then another, then another…• Protein Phosphatase lead to• dephosphorylation

Second Messengers- Cyclic AMP• Cyclic Adenosine Monophosphate• Water Soluble- Spread through diffusion• Adenylyl Cyclase & Epinephrine• G proteins

Benefits of Multistep system• Amplification of signal

• More coordinated and regulated

Response

Response• Occurs in nucleus or cytoplasm• Transcription factors• Multiple responses to the same signal• Scaffolding proteins