Ctr2 regulates biogenesis of a cleaved form of mammalian Ctr1 metal transporter lacking the copper- and cisplatin-binding ecto-domain

Abstract

Significance Copper is essential for normal growth and development because it serves roles in catalysis, signaling, and structure. Cells acquire copper through the copper transporter 1 (Ctr1) protein, a copper transporter that localizes to the cell membrane and intracellular vesicles. Both copper and the anticancer drug cisplatin are imported by Ctr1 by virtue of an extracellular domain rich in metal-binding amino acids. In this report we demonstrate that a protein structurally related to Ctr1, called Ctr2, plays a role in the generation or stability of a truncated form of Ctr1 lacking a large portion of the extracellular domain. Retention of this domain in mice or cells lacking Ctr2 enhances copper and cisplatin uptake, thereby establishing Ctr2 as a regulator of Ctr1 function.

Reciprocal functions of Cryptococcus neoformans copper homeostasis machinery during pulmonary infection and meningoencephalitis

“…5A,B), suggesting that these Cu þ transporters undergo post-translational modification. In mammals, the Ctr1 Cu þ transporter is glycosylated at two positions within the N terminus [20][21][22][23] . We used a protein deglycosylation enzyme mix that removes both N-and O-glycosylation to determine whether C. neoformans Cu transporters are glycosylated.…”

Cathepsin Protease Controls Copper and Cisplatin Accumulation via Cleavage of the Ctr1 Metal-binding Ectodomain

“…1A) (32). Ctr2 forms a complex with Ctr1 in vivo and positively influences the abundance of the tCtr1 species.…”

“…To explore which of these protease families is relevant for the formation of tCtr1, proteases were evaluated for co-localization with Ctr1 and Ctr2. Ctr1 has been shown to continuously cycle between the plasma membrane and endocytic vesicles, where it localizes to endolysosomal compartments that also harbor Ctr2 (14,30,32,35). Because Ctr1 cleavage has previously been suggested to occur at an endosomal compartment (30), subcellular fractionation was carried out in an attempt to localize Ctr1 with the appropriate protease.…”

“…Previously, an integral membrane protein similar to Ctr1, denoted Ctr2, was shown to both interact with and regulate the ratio of full-length Ctr1 to tCtr1 in mouse embryonic fibroblasts (MEFs) and in specific tissues in Ctr2 knock-out mice (32). In the absence of Ctr2, MEFs possess dramatically lower levels of tCtr1, while simultaneously expressing high levels of full-length Ctr1 and accumulating Cu ϩ and cisplatin.…”

“…In the absence of Ctr2, MEFs possess dramatically lower levels of tCtr1, while simultaneously expressing high levels of full-length Ctr1 and accumulating Cu ϩ and cisplatin. A large fraction of the Cu ϩ accumulated in Ctr2 Ϫ/Ϫ MEFs and mouse tissues is found in endosomal compartments (32). The mechanism by which Ctr2 governs the abundance of tCtr1, thereby controlling Cu ϩ and cisplatin accumulation, and the subcellular location in which this process occurs have not been elucidated.…”