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Updated: May 14, 2026
10:17
A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
Published on: April 29, 2022
Protein phosphatase 2A dephosphorylates CaBP4 and regulates CaBP4 function.
Françoise Haeseleer1, Izabela Sokal, Frederick D Gregory
1Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA. fanfan@u.washington.edu
Investigative Ophthalmology & Visual Science
|January 24, 2013
Summary
Protein phosphatase 2A (PP2A) dephosphorylates CaBP4 in the retina, regulating Ca(2+) channel function. This finding reveals a novel role for phosphatases in fine-tuning presynaptic Ca(2+) signals at the photoreceptor synapse.
Area of Science:
- Neuroscience
- Molecular Biology
- Cellular Signaling
Background:
- Calcium-binding protein 4 (CaBP4) is crucial for photoreceptor synaptic function in the retina.
- CaBP4 phosphorylation by protein kinase C zeta (PKCζ) at serine 37 modulates its interaction with voltage-gated Ca(v)1 Ca(2+) channels.
Purpose of the Study:
- To investigate the role and significance of protein phosphatase 2A (PP2A) in CaBP4 dephosphorylation.
- To understand how PP2A regulates CaBP4 function in the retina.
Main Methods:
- In vitro assays measuring CaBP4 dephosphorylation with phosphatase inhibitors and PP2A subunit overexpression.
- Pull-down experiments to assess CaBP4 and PP2A subunit association.
- Electrophysiological recordings to analyze the impact of CaBP4 dephosphorylation on Ca(v)1.3 currents.
Main Results:
- PP2A inhibitors (okadaic acid, fostriecin) blocked CaBP4 dephosphorylation in retinal lysates.
- Increased phosphatase activity under light conditions reversed CaBP4 phosphorylation.
- PP2A overexpression enhanced CaBP4 dephosphorylation, while inhibition potentiated CaBP4's effect on Ca(v)1.3 channels.
Conclusions:
- CaBP4 is dephosphorylated by PP2A in the retina.
- Protein phosphatases play a novel role in regulating CaBP4 function.
- This regulation fine-tunes presynaptic Ca(2+) signals at the photoreceptor synapse.
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