Positive charge forces cations such as Mg++ and Ca++ to diffuse from the tubular lumen through the paracellular space and into the interstitial fluid.

TLS Online TPP Program

#Id: 9067

#Unit 4. Cell Communication and Cell Signaling

Phosphorylated CREB binds to CRE-containing target genes and also binds to the co-activator termed CBP/P300, thereby stimulating gene transcription

TLS Online TPP Program

#Id: 9068

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 9069

#Unit 4. Cell Communication and Cell Signaling

Inactive PKA is a tetramer consisting of- 

two regulatory (R) subunits

two catalytic (C) subunits

TLS Online TPP Program

#Id: 9070

#Unit 4. Cell Communication and Cell Signaling

Two large classes of GTPase switch proteins are used in signal transduction pathways:

1. Heterotrimeric G proteins

2. Monomeric G proteins

TLS Online TPP Program

#Id: 9071

#Unit 4. Cell Communication and Cell Signaling

Feedback mechanisms suppress signaling by the PKA pathway:

1. Intrinsic GTPase activity of Gαs

2. PDE acts to hydrolyze cAMP to 5′-AMP

3. By BARK

TLS Online TPP Program

#Id: 9072

#Unit 4. Cell Communication and Cell Signaling

In resting state 

basal level of PDE activity keeps cAMP levels below those necessary for PKA activation.