Smaardijk S, Chen J, Kerselaers S, Voets T, Eggermont J, Vangheluwe P. Store-independent coupling between the Secretory Pathway Ca
2+ transport ATPase SPCA1 and Orai1 in Golgi stress and Hailey-Hailey disease.
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018;
1865:855-862. [PMID:
29555205 DOI:
10.1016/j.bbamcr.2018.03.007]
[Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/10/2018] [Accepted: 03/14/2018] [Indexed: 01/10/2023]
Abstract
The Secretory Pathway Ca2+ ATPases SPCA1 and SPCA2 transport Ca2+ and Mn2+ into the Golgi and Secretory Pathway. SPCA2 mediates store-independent Ca2+ entry (SICE) via STIM1-independent activation of Orai1, inducing constitutive Ca2+ influx in mammary epithelial cells during lactation. Here, we show that like SPCA2, also the overexpression of the ubiquitous SPCA1 induces cytosolic Ca2+ influx, which is abolished by Orai1 knockdown and occurs independently of STIM1. This process elevates the Ca2+ concentration in the cytosol and in the non-endoplasmic reticulum (ER) stores, pointing to a functional coupling between Orai1 and SPCA1. In agreement with this, we demonstrate via Total Internal Reflection Fluorescence microscopy that Orai1 and SPCA1a co-localize near the plasma membrane. Interestingly, SPCA1 overexpression also induces Golgi swelling, which coincides with translocation of the transcription factor TFE3 to the nucleus, a marker of Golgi stress. The induction of Golgi stress depends on a combination of SPCA1 activity and SICE, suggesting a role for the increased Ca2+ level in the non-ER stores. Finally, we tested whether impaired SPCA1a/Orai1 coupling may be implicated in the skin disorder Hailey-Hailey disease (HHD), which is caused by SPCA1 loss-of-function. We identified HHD-associated SPCA1a mutations that impair either the Ca2+ transport function, Orai1 activation, or both, while all mutations affect the Ca2+ content of the non-ER stores. Thus, the functional coupling between SPCA1 and Orai1 increases cytosolic and intraluminal Ca2+ levels, representing a novel mechanism of SICE that may be affected in HHD.
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