Human Keratinocyte ATP2C1 Localizes to the Golgi and Controls Golgi Ca2+ Stores

Abstract

Hailey-Hailey disease (MIM16960) is a blistering skin disease caused by mutations in the Ca2+ ATPase ATP2C1. We found that the abnormal Ca2+ signaling seen in Hailey-Hailey disease keratinocytes correlates with decreased protein levels of ATP2C1. Human ATP2C1 protein approximated 115 kDa in size. The ATP2C1 is localized to the Golgi apparatus in human keratinocytes, similar to its localization in yeast and Caenorhabditis elegans. To test whether the ATP2C1 controls Golgi Ca2+ stores, we measured intraorganelle Ca2+ concentrations using specifically targeted aequorins. Whereas normal keratinocytes display Golgi Ca2+ levels comparable to other epithelial cells, Hailey-Hailey disease keratinocyte Golgi Ca2+ refill is slower, and the maximum Ca2+ concentration reached is significantly lower. These findings were replicated in vivo, because clinically normal Hailey-Hailey disease epidermis contained lower Ca2+ stores and displayed an abnormal Ca2+ gradient. In this report we localize the ATP2C1, demonstrate its physiologic relevance in mammalian cells, and measure intraorganelle Golgi Ca2+ in keratinocytes.

Functional expression of heterologous proteins in yeast: insights into Ca2+ signaling and Ca2+-transporting ATPases

“…In addition, pmr1 mutants have elevated resting levels of Ca 2ϩ in the cytosol and cannot effectively maintain cellular Ca 2ϩ and Mn 2ϩ homeostasis (33,35,62). These phenotypes are strikingly similar to observations in keratinocytes isolated from HHD patients that show higher levels of resting cytosolic Ca 2ϩ , defects in recovery from a Ca 2ϩ load (36), and significant decreases in luminal Ca 2ϩ (5). Thus the molecular defects in HHD may be linked to either insufficient Ca 2ϩ and Mn 2ϩ in the Golgi or defective cytosolic Ca 2ϩ clearance, or more likely, both.…”

“…Pmr1 homologs are now known to be ubiquitous in all higher eukaryotes, with the notable exception of plants, and much of what we know about the structure and physiological role of these transporters comes from studies in yeast. More recently, these studies have extended to SPCA homologs from humans (5,27,83), Caenorhabditis elegans (13,87), and rats (Ref. 69; reviewed in Ref.…”

“…In mammalian cells, PI turnover leads to activation of protein kinase C by diacylglycerol and intracellular Ca 2ϩ release by IP 3 . Curiously, in yeast, IP 3 appears to be rapidly converted to polyphosphates (IP 4 , IP 5 , and IP 6 ), and although there are no known IP 3 receptor channels, genetic disruption of IP 3 kinases enhances the Ca 2ϩ signal (81).…”

Newly characterized Golgi-localized family of proteins is involved in calcium and pH homeostasis in yeast and human cells

“…For example, mutation of secretory pathway Ca 2+ -ATPase isoform 1 (SPCA1), the human ortholog of yeast PMR1, causes a rare autosomaldominant skin disorder, called Hailey-Hailey disease, which is accompanied by an increase of the [Ca 2+ ] cyt and a reduction in the Golgi luminal Ca 2+ concentration (19,34,35). Mutations in the a2 subunit of the V-type H + ATPase, encoded by ATP2V0A2, have also been shown to result in abnormal glycosylation (CDG) and skin diseases (7,36).…”

Pemphigus Vulgaris IgG and Methylprednisolone Exhibit Reciprocal Effects on Keratinocytes

“…For example, PV IgG-induced decrease of proton ATPase might lead to alterations in keratinocyte adhesion via mechanisms that cause acantholysis in HaileyHailey and Darier diseases, both of which are associated with ATP-powered pump mutations (89,90). It has been reported recently that in the epidermis of patients with Hailey-Hailey disease abnormal ATP and Ca 2ϩ levels are linked to defects in actin reorganization, which is necessary for normal cell-to-cell adhesion in KC (91,92).…”