Mechanism of Mn detection via SPCA1 and GPP130. Endocytosed vesicles containing GPP130 are typically sorted directly to the late Golgi. SPCA1 transports Mn into the Golgi complex. In the presence of Mn and GPP130, vesicles are either guided to lysosomes, where Mn is then sequestered, or are brought to the membrane, where Mn is then exocytosed. Abbreviations: GPP, cis-Golgi glycoprotein; Mn, manganese; SPCA1, secretory pathway Ca2+-ATPase isoform 1.