Phosphatases control PKA-dependent functional microdomains at the outer mitochondrial membrane

Area of Science:

• Cellular signaling
• Molecular biology
• Biochemistry

Background:

• Cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) signaling heterogeneity is often linked to enzyme localization.
• The role of phosphatases in generating signaling heterogeneity, even with uniform cAMP levels, remains understudied.

Purpose of the Study:

• To investigate if phosphatase distribution, rather than cAMP gradients, can create distinct cAMP/PKA signaling domains.
• To explore the impact of phosphatase activity on PKA-dependent phosphorylation in different cellular compartments.

Main Methods:

• Utilized Förster resonance energy transfer (FRET)-based sensors to measure cAMP and PKA activity in real-time.
• Compared signaling in the cytosol and outer mitochondrial membrane (OMM) of primary rat cardiomyocytes.
• Assessed phosphatase-dependent dephosphorylation rates and their effect on PKA targets.

Main Results:

• Comparable cAMP increases led to higher PKA-dependent phosphorylation in the OMM compared to the cytosol.
• This difference was more pronounced with small, physiological cAMP changes.
• Phosphatase activity differentially regulated PKA-driven activation of CREB and mitochondrial elongation.

Conclusions:

• Subcellular phosphatase distribution can generate functionally distinct cAMP/PKA signaling domains independently of cAMP gradients.
• The accessibility of substrates to phosphatases influences the extent of PKA-mediated phosphorylation.
• Phosphatases play a critical role in sculpting localized cellular responses to cAMP/PKA signaling.