PIKfyve upregulates CFTR activity

Area of Science:

• Molecular biology
• Cell physiology
• Ion channel function

Background:

• The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated chloride channel crucial for epithelial function.
• Mutations, like (DeltaF508)CFTR, cause cystic fibrosis, characterized by impaired chloride secretion.
• CFTR activity is modulated by kinases, including SGK1, which interacts with PIKfyve and PKB/Akt.

Purpose of the Study:

• To investigate whether PKB/Akt and PIKfyve act as regulators of CFTR function.
• To determine if these regulators affect both wild-type CFTR and the common disease-causing mutant (DeltaF508)CFTR.

Main Methods:

• Expression of CFTR or (DeltaF508)CFTR in Xenopus oocytes.
• Co-expression with PKB/Akt, PIKfyve, or a kinase-resistant PIKfyve mutant ((S318A)PIKfyve).
• Measurement of cAMP-induced chloride current (I(cAMP)) using dual electrode voltage clamp and assessment of protein abundance via immunohistochemistry.

Main Results:

• Forskolin/IBMX stimulation activated I(cAMP) in CFTR-expressing oocytes, but not in those with (DeltaF508)CFTR.
• Co-expression of PKB/Akt and PIKfyve significantly increased I(cAMP) in CFTR-expressing oocytes (2-3 fold), but not in (DeltaF508)CFTR oocytes.
• PIKfyve, but not (S318A)PIKfyve, enhanced CFTR protein levels, indicating a role in protein stability or trafficking.

Conclusions:

• PKB/Akt and PIKfyve are identified as novel regulators of functional CFTR.
• These regulators specifically enhance wild-type CFTR activity and protein abundance.
• The findings suggest a potential therapeutic strategy targeting PKB/Akt and PIKfyve for cystic fibrosis.