Ca2+-activated K+ channel-associated phosphatase and kinase activities during development

Area of Science:

• Biochemistry
• Molecular Biology
• Physiology

Background:

• Fetal ovine basilar artery smooth muscle cells (SMCs) exhibit higher "big" calcium-activated potassium (BK) channel activity and a lower calcium setpoint compared to adult SMCs.
• Developmental regulation of ion channel function is crucial for tissue maturation and adaptation.

Purpose of the Study:

• To investigate the hypothesis that developmental differences in BK channel activity and calcium setpoint in ovine basilar artery SMCs are due to regulated phosphorylation.
• To elucidate the role of channel-associated protein phosphatases and kinases (CAPAKs) in mediating these developmental changes.

Main Methods:

• Utilized the patch-clamp technique to measure BK channel voltage activation in SMC inside-out patch preparations.
• Employed a novel in situ enzymological approach to selectively activate and inhibit CAPAKs.
• Compared BK channel activity and CAPAK activity between fetal and adult ovine basilar artery SMCs.

Main Results:

• Demonstrated that BK channel activity is modulated by differential phosphorylation during development.
• Observed significant developmental changes in the activities of CAPAKs.
• Found greater protein kinase A activity in adult SMCs, while fetal SMCs showed higher protein kinase G and phosphatase activity.

Conclusions:

• Developmentally regulated phosphorylation, influenced by differential CAPAK activities, underlies the distinct BK channel characteristics in fetal versus adult ovine basilar artery SMCs.
• The findings suggest a biochemical mechanism for the observed differences in BK channel calcium setpoint.
• The functional stoichiometry of CAPAKs likely varies during development, representing a novel mechanism for ion channel regulation.