Question

On a sheet of paper, write the entire sequence of signal transduction events in the
TGF-β signaling pathway.

Exterior TGFB RII RIO I Cytosol MHZ Smad3 C Smad3-P NUS MH1 -Smad4 - Imp-B Smad4 Nudeus Smad WAGACAGACIU _ TFE3 Transcription PAI-1 AGAC, CACGTGM 3-bp spacer

Answer 1

Sequence of signal transduction events in the TGF-β signaling pathway:

1a) TGF-β ligand is binding to the ligand binding domain of type III TGF-β receptor (transmembrane receptor)

1b) TGF -β ligand is binding to ligand binding domain of type II TGF-β receptor and induces autophosphorylation.

2) Type I receptor is having kinase action, which gets phosphorylated and forms tetrameric complex with type II receptor.

3) Smad3 gets cross phophorylated and become active.

4) Phosphorylated Smad3 binds to Smad4   and NLS of Smad3 is attached to importin-β and forms Smad complx (heterooligomeric complex)

5) importin-β guides entry of Smad complex to the nucleus

6) importin-β will become free from Smad complx and binds to Ran-GTP

7) Smad complex binds to the Transcription factor TFE3 and and regulates gene expression.