Structural Basis of the Oncogenic Interaction of Phosphatase PRL-1 with the Magnesium Transporter CNNM2

Abstract

Edited by Roger J. ColbranPhosphatases 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 (CNNM2 BAT ), which consists of two cystathionine ␤-synthase (CBS) domains (IPR000664) and represents an intracellular regulatory module of the transporter. The structure reveals a heterotetrameric association, consisting of a disclike homodimer of CNNM2 BAT 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 Mg 2؉ 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.

Therapeutic Targeting of Oncogenic Tyrosine Phosphatases

“…1C; refs. 28–31). To uncover the in vivo function of PRLs, gene knockout was employed to study the effect of PRL deletion at the organismal level.…”

Physiological and oncogenic roles of the PRL phosphatases

“…An independent report by a second group also showed this unexpected molecular association [184]. This interaction was further validated by structural studies, which characterized the interactions between both proteins [23,25,185]. The CNNMs, previously known as ancient conserved domain protein (ACDP), are found expressed in mammals and are evolutionary conserved from unicellular to multicellular organisms [186,187].…”

“…. Moreover, this aspartic acid plays a substrate analog‐like role on the active site of PRLs, hence the binding through the Bateman domain was seen to inhibit the in vitro phosphatase activity .…”

“…Moreover, the T568I mutation of CNNM2 mimics the effect of nucleotide binding and locks it in the flat conformation . The binding of PRLs to the CNNMs was also shown to favor the flat conformation through electrostatic attraction between the surfaces of the two proteins . This intracellular conformational change is believed to affect the transmembrane domains of CNNMs and modulate ion transport.…”

“…More precisely, the binding occurs at the tip of their elongated loop, which requires the presence of an evolutionary conserved aspartic acid residue, located in their second CBS domain [44,184,185,189]. This intracellular domain was also shown to interact with AMP, ADP, ATP, and Mg-ATP, which induces a conformational change in CNNMs and can contribute to their Mg sensing/transport abilities [185,[190][191][192]. Structural studies have unraveled the effect of Mg and nucleotide binding on the conformation of CNNMs.…”