Identification of a gain-of-function mutation in a Golgi P-type ATPase that enhances Mn²⁺ efflux and protects against toxicity

P-type ATPases transport a wide array of ions, regulate diverse cellular processes, and are implicated in a number of human diseases. However, mechanisms that increase ion transport by these ubiquitous proteins are not known. SPCA1 is a P-type pump that transports Mn²⁺ from the cytosol into the Golgi. We developed an intra-Golgi Mn²⁺ sensor and used it to screen for mutations introduced in SPCA1, on the basis of its predicted structure, which could increase its Mn²⁺ pumping activity. Remarkably, a point mutation (Q747A) predicted to increase the size of its ion permeation cavity enhanced the sensor response and a compensatory mutation restoring the cavity to its original size abolished this effect. In vivo and in vitro Mn²⁺ transport assays confirmed the hyperactivity of SPCA1-Q747A. Furthermore, increasing Golgi Mn²⁺ transport by expression of SPCA1-Q747A increased cell viability upon Mn²⁺ exposure, supporting the therapeutic potential of increased Mn²⁺ uptake by the Golgi in the management of Mn²⁺-induced neurotoxicity.