Phosphoinositide phosphatase activity coupled to an intrinsic voltage sensor

Area of Science:

• Molecular Biology
• Cell Physiology
• Biochemistry

Background:

• Membrane potential fluctuations influence cellular processes via ion channels and transporters.
• The mechanisms of other membrane potential-coupled signaling pathways remain largely unknown.

Purpose of the Study:

• To identify and characterize novel proteins that link membrane potential to cellular signaling.
• To elucidate the function and mechanism of a newly discovered voltage-sensing protein.

Main Methods:

• Cloning and expression of the novel protein from Ciona intestinalis.
• Electrophysiological recordings to detect gating currents.
• Biochemical assays to measure phosphoinositide turnover.
• Immunocytochemistry to determine protein localization.

Main Results:

• A novel protein, C. intestinalis voltage-sensor-containing phosphatase (Ci-VSP), was identified with a voltage-sensing domain and phosphatase activity.
• Ci-VSP exhibits channel-like gating currents, directly translating membrane potential changes into phosphoinositide turnover.
• The phosphatase activity of Ci-VSP is regulated by physiological membrane potential ranges.
• Ci-VSP is localized to the sperm tail membranes in Ciona, suggesting a role in sperm function.

Conclusions:

• Voltage sensing is not exclusive to ion channels and can be integrated into other protein types.
• Ci-VSP represents a novel mechanism for translating electrical signals into biochemical events.
• The discovery of Ci-VSP broadens the understanding of voltage sensing's ubiquity and functional diversity in biological systems.