The synthesis and secretion of steroid hormones by the adrenal cortex depend on the stimulation of cholesterol desmolase by ACTH.

TLS Online TPP Program

#Id: 9348

#Unit 4. Cell Communication and Cell Signaling

3 separate TGF-β receptor proteins participate in binding TGF-β and activating signaling:

RI, RII, and RIII

TLS Online TPP Program

#Id: 9350

#Unit 4. Cell Communication and Cell Signaling

RI and RII receptors are homodimeric proteins with serine/threonine kinases in their cytosolic domains. 

(RI and RII sufficient to serve as a functional hetero-tetrameric TGF-β receptor)

TLS Online TPP Program

#Id: 9351

#Unit 4. Cell Communication and Cell Signaling

RII exhibits constitutive kinase activity; means it is active even when not bound to TGF-β.

TLS Online TPP Program

#Id: 9352

#Unit 4. Cell Communication and Cell Signaling

RIII, also called β-glycan, is a cell-surface proteoglycan.

TLS Online TPP Program

#Id: 9353

#Unit 4. Cell Communication and Cell Signaling

The function of RIII for TGF-β receptors is similar to that of the α subunit of the IL-2 receptor 

(means facilitating TGF-β binding to the RII and RI)

   

         

TLS Online TPP Program

#Id: 9355

#Unit 4. Cell Communication and Cell Signaling

Most cells lack RIII, TGF-β binds directly to the RII

dimer, but Active RII kinase activity is not sufficient to generate an intracellular signal