The Three Stages of Cell Signaling By: Madeline Meyer and Carlos Sanchez ReceptionTransductionResponse

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

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