Capacitation

The sperm cell membrane

is altered by the removal of

cholesterol by albumin proteins in the female reproductive tract

TLS Online TPP Program

#Id: 9360

#Unit 4. Cell Communication and Cell Signaling

Smad2/3 become phosphorylated by active RI receptors and together with Smad4 move into the nucleus to activate gene transcription

TLS Online TPP Program

#Id: 9361

#Unit 4. Cell Communication and Cell Signaling

R-Smads comprising: 

An N-terminal MH1 domain

A central proline-rich linker 

A C-terminal MH2 domain

TLS Online TPP Program

#Id: 9362

#Unit 4. Cell Communication and Cell Signaling

MH1 domain contains:

DNA binding segment Nuclear-localization signal

TLS Online TPP Program

#Id: 9363

#Unit 4. Cell Communication and Cell Signaling

Phosphorylation of two serines in Ser-X-Ser motif at the extreme C-terminus of the MH2 domain by the activated RI separates the two domains, exposing the NLS for binding to importins

TLS Online TPP Program

#Id: 9364

#Unit 4. Cell Communication and Cell Signaling

Simultaneously, two serines in each Smad2/3 phosphorylated by RI receptor kinase bind to phosphoserine-binding sites in the MH2 domains of a Smad4

TLS Online TPP Program

#Id: 9365

#Unit 4. Cell Communication and Cell Signaling

Inside the nucleus, R smad-co smad complex binds to nuclear transcription factor TFE3 to activate transcription of PAI-1 & other ECM proteins such as fibronectin & collagens