Abstract
Phosphatases of regenerating liver (PRLs), the most oncogenic of all protein-tyrosine phosphatases (PTPs), play a critical role in metastatic progression of cancers. Recent findings established a new paradigm by uncovering that their association with magnesium transporters of the cyclin M (CNNM) family causes a rise in intracellular magnesium levels that promote oncogenic transformation. Recently, however, essential roles for regulation of the circadian rhythm and reproduction of the CNNM family have been highlighted. Here, we describe the crystal structure of PRL-1 in complex with the Bateman module of CNNM2 (CNNM2BAT), which consists of two cystathionine β-synthase (CBS) domains (IPR000664) and represents an intracellular regulatory module of the transporter. The structure reveals a heterotetrameric association, consisting of a disc-like homodimer of CNNM2BAT bound to two independent PRL-1 molecules, each one located at opposite tips of the disc. The structure highlights the key role played by Asp-558 at the extended loop of the CBS2 motif of CNNM2 in maintaining the association between the two proteins and proves that the interaction between CNNM2 and PRL-1 occurs via the catalytic domain of the phosphatase. Our data shed new light on the structural basis underlying the interaction between PRL phosphatases and CNNM transporters and provides a hypothesis about the molecular mechanism by which PRL-1, upon binding to CNNM2, might increase the intracellular concentration of Mg2+ thereby contributing to tumor progression and metastasis. The availability of this structure sets the basis for the rational design of compounds modulating PRL-1 and CNNM2 activities.
Highlights
Phosphatases of regenerating liver (PRLs), the most oncogenic of all protein-tyrosine phosphatases (PTPs), play a critical role in metastatic progression of cancers
Recent findings established a new paradigm by uncovering that their association with magnesium transporters of the cyclin M (CNNM) family causes a rise in intracellular magnesium levels that promote oncogenic transformation
Based on previous findings showing that all PRLs interact with CNNM3 [17] and CNNM4 [18], and by taking into account the close sequence homology and possibly similar functions shared by cation transport mediator” (CNNM), we first assessed whether CNNM2 interacts with all three PRL members
Summary
CNNM2 Associates with All Three PRLs—The association of PRLs with the CNNMs has been demonstrated to control the intracellular magnesium levels, but whether all PRL members have the same mechanism of action still remains to be elucidated. Based on previous findings showing that all PRLs interact with CNNM3 [17] and CNNM4 [18], and by taking into account the close sequence homology (supplemental Fig. S1) and possibly similar functions shared by CNNMs, we first assessed whether CNNM2 interacts with all three PRL members. We used the full-length human PRL proteins and an engineered protein construct, CNNM2BAT [39], comprising residues 429 –584 and containing the Bateman module of CNNM2 and the preceding ␣-helix (H0) that connect to the DUF21 transmembrane domain We found that the three potential PRLs-CNNM2BAT complexes are formed (Fig. 1). Pure CNNM2BAT eluted as a dimer (Fig. 1), as we described previously [37]. Additional experiments co-transfecting V5-tagged full-length CNNM2 and GST-tagged PRL-1, -2, and -3 in HeLa cells, followed by GST pulldown, supported the ability of CNNM2 to bind all PRL members (Fig. 1)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
