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Open Access Highly Accessed Research article

Intracellular calcium release modulates polycystin-2 trafficking

Ayako Miyakawa12, Cristián Ibarra1, Seth Malmersjö1, Anita Aperia3, Peter Wiklund2 and Per Uhlén1*

Author Affiliations

1 Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77, Stockholm, Sweden

2 Department of Molecular Medicine and Surgery, Karolinska University Hospital, SE-171 76, Stockholm, Sweden

3 Department of Woman and Child Health, Astrid Lindgren Children’s Hospital Q2:09, Karolinska University Hospital, SE-171 76, Stockholm, Sweden

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BMC Nephrology 2013, 14:34  doi:10.1186/1471-2369-14-34

Published: 11 February 2013

Abstract

Background

Polycystin-2 (PC2), encoded by the gene that is mutated in autosomal dominant polycystic kidney disease (ADPKD), functions as a calcium (Ca2+) permeable ion channel. Considerable controversy remains regarding the subcellular localization and signaling function of PC2 in kidney cells.

Methods

We investigated the subcellular PC2 localization by immunocytochemistry and confocal microscopy in primary cultures of human and rat proximal tubule cells after stimulating cytosolic Ca2+ signaling. Plasma membrane (PM) Ca2+ permeability was evaluated by Fura-2 manganese quenching using time-lapse fluorescence microscopy.

Results

We demonstrated that PC2 exhibits a dynamic subcellular localization pattern. In unstimulated human or rat proximal tubule cells, PC2 exhibited a cytosolic/reticular distribution. Treatments with agents that in various ways affect the Ca2+ signaling machinery, those being ATP, bradykinin, ionomycin, CPA or thapsigargin, resulted in increased PC2 immunostaining in the PM. Exposing cells to the steroid hormone ouabain, known to trigger Ca2+ oscillations in kidney cells, caused increased PC2 in the PM and increased PM Ca2+ permeability. Intracellular Ca2+ buffering with BAPTA, inositol 1,4,5-trisphosphate receptor (InsP3R) inhibition with 2-aminoethoxydiphenyl borate (2-APB) or Ca2+/Calmodulin-dependent kinase inhibition with KN-93 completely abolished ouabain-stimulated PC2 translocation to the PM.

Conclusions

These novel findings demonstrate intracellular Ca2+-dependent PC2 trafficking in human and rat kidney cells, which may provide new insight into cyst formations in ADPKD.

Keywords:
Polycystin-2; Protein trafficking; Calcium signaling; Kidney cells; Autosomal dominant polycystic kidney disease