Investigating the functional link between TMEM165 and SPCA1

Abstract

TMEM165 was highlighted in 2012 as the first member of the Uncharacterized Protein Family 0016 (UPF0016) related to human glycosylation diseases. Defects in TMEM165 are associated with strong Golgi glycosylation abnormalities. Our previous work has shown that TMEM165 rapidly degrades with supraphysiological manganese supplementation. In this paper, we establish a functional link between TMEM165 and SPCA1, the Golgi Ca2+/Mn2+ P-type ATPase pump. A nearly complete loss of TMEM165 was observed in SPCA1-deficient Hap1 cells. We demonstrate that TMEM165 was constitutively degraded in lysosomes in the absence of SPCA1. Complementation studies showed that TMEM165 abundance was directly dependent on SPCA1's function and more specifically its capacity to pump Mn2+ from the cytosol into the Golgi lumen. Among SPCA1 mutants that differentially impair Mn2+ and Ca2+ transport, only the Q747A mutant that favors Mn2+ pumping rescues the abundance and Golgi subcellular localization of TMEM165. Interestingly, the overexpression of SERCA2b also rescues the expression of TMEM165. Finally, this paper highlights that TMEM165 expression is linked to the function of SPCA1.

From the Uncharacterized Protein Family 0016 to the GDT1 family: Molecular insights into a newly-characterized family of cation secondary transporters

“…Like in yeast, TMEM165 genetically interacts with the human ortholog of Pmr1p, the Golgi Ca 2+ -Mn 2+ ATPase SPCA1, in the way that the abundance of TMEM165 depends on the abundance and function of SPCA1. The authors of this study even suggest that SPCA1 and TMEM165 physically interact [ 25 ]. Interestingly, in mice, the level of expression of TMEM165 in lactating mammary tissues increases by a 25-fold factor during lactation while forced cessation of lactation leads to a rapid decrease of its expression.…”

SPCA1 governs the stability of TMEM165 in Hailey-Hailey disease

“…According to our recent results in Hap1 cells, a proximity between TMEM165 and SPCA1 was shown [12]. Although the subcellular localization of these two proteins is not affected, it could well be that SP-CA1 mutations could prevent the proximity with TMEM165.…”

“…Fibroblasts from 4 Hailey-Hailey disease patients (HHD 1 to 4) and two control human fibroblasts (NHF 1 and 2) were first used. Using anti-SPCA1 antibody, whose detection specificity was previously assessed [12], a major band at 100 kDa, corresponding to the molecular weight of SPCA1, was detected in all HHD and control fibroblasts (Fig. 1A).…”

“…By using KO SPCA1 cells, we recently highlighted that TMEM165 expression was dependent on SPCA1 capacity to import Mn 2+ into the Golgi lumen [12]. In Hailey-Hailey disease patients' cells, SPCA1 is partially deficient due to a loss of one functional copy of ATP2C1 gene.…”

“…Interestingly, our team recently demonstrated a functional link between SPCA1 and another Golgi protein named TMEM165 [12]. TMEM165 belongs to an uncharacterized family of transmembrane proteins, named UPF0016 (Uncharacterized Protein Family 0016) and possesses 7 transmembrane domains.…”