Effect of Hailey-Hailey Disease Mutations on the Function of a New Variant of Human Secretory Pathway Ca2+/Mn2+-ATPase (hSPCA1) (original) (raw)

2003, Journal of Biological Chemistry

ATP2C1, encoding the human secretory pathway Ca 2؉ /Mn 2؉ ATPase (hSPCA1), was recently identified as the defective gene in Hailey-Hailey Disease (HHD), an autosomal dominant skin disorder characterized by persistent blisters and erosions. To investigate the underlying cause of HHD, we have analyzed the changes in expression level and function of hSPCA1 caused by mutations found in HHD patients. Mutations were introduced into hSPCA1d, a novel splice variant expressed in keratinocytes, described here for the first time. Encoded by the full-length of optional exons 27 and 28, hSPCA1d was longer than previously identified splice variants. The protein competitively transported Ca 2؉ and Mn 2؉ with equally high affinity into the Golgi of COS-1 cells. Ca 2؉-and Mn 2؉-dependent phosphoenzyme intermediate formation in forward (ATP-fuelled) and reverse (P ifuelled) directions was also demonstrated. HHD mutant proteins L341P, C344Y, C411R, T570I, and G789R showed low levels of expression, despite normal levels of mRNA and correct targeting to the Golgi, suggesting instability or abnormal folding of the mutated hSPCA1 polypeptides. P201L had little effect on the enzymatic cycle, whereas I580V caused a block in the E 1 ϳP 3 E 2-P conformational transition. D742Y and G309C were devoid of Ca 2؉-and Mn 2؉-dependent phosphoenzyme formation from ATP. The capacity to phosphorylate from P i was retained in these mutants but with a loss of sensitivity to both Ca 2؉ and Mn 2؉ in D742Y and a preferential loss of sensitivity to Mn 2؉ in G309C. These results highlight the crucial role played by Asp-742 in the architecture of the hSPCA1 ion-binding site and reveal a role for Gly-309 in Mn 2؉ transport selectivity. At present, three distinct classes of phosphorylation-type Ca 2ϩ transport ATPases have been identified in mammalian * This work was supported in part by the Wellcome Trust. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.