* Wnt proteins bind to frizzled receptors and inhibit the degradation of -catenin

Extracellular signal molecule

Receptor protein

Intracellular signaling proteins

Target proteins

Metabolic enzyme

Gene regulatory protein

Cytoskeletal protein

Extracelluar signal

molecules bind to specific receptors

Three classes of cell-surface receptors

oror

Gene transcription is activated by a rise in cAMP conc

Relay protein

Amplifier and transducer protein

Messenger protein

MAP-kinase serine/threonine phosphorylation pathway activated by

Ras

Raf

MEK

MAPK

Cytokine receptors activate the Jak-STAT signaling pathway

JAKsJAK1JAK2JAK3Tyk2

Signal transducers and activators of transcription

* Wnt proteins bind to frizzled receptors and inhibit the degradation of -catenin