No abstract

The phosphatases of regenerating liver (PRLs) are involved in tumorigenesis and metastatic cancer yet their cellular function remains unclear. Recent reports have shown PRL phosphatases bind tightly to the CNNM family of membrane proteins to regulate magnesium efflux. Here, we characterize the interactions between the CBS-pair (Bateman) domain of CNNM3 and either PRL2 or PRL3 using X-ray crystallography, isothermal titration calorimetry, and activity assays. We report four new crystal structures of PRL proteins bound to the CNNM3 CBS-pair domain that reveal the effects of cysteine disulphide formation and nucleotide binding on complex formation. We use comprehensive mutagenesis of the PRL3 catalytic site to quantify the importance of different PRL amino acids, including cysteine 104, leucine 108, and arginine 110, for CNNM binding and phosphatase activity. We show the PRL3 R138E mutant is selectively deficient in CNNM3 binding with the potential to distinguish between the downstream effects of phosphatase and CNNM-binding activities in vivo. Through a novel activity assay, we show that PRL3 has magnesium-sensitive phosphatase activity with ATP and other nucleotides. Our results identify a strong correlation between phosphatase activity and CNNM binding and support the contention that PRL function as pseudophosphatases regulated by chemical modifications of their catalytic cysteine.

Van der Waals (vdW) heterostructures, stacking different two-dimensional materials, have opened up unprecedented opportunities to explore new physics and device concepts. Especially interesting are recently discovered two-dimensional magnetic vdW materials, providing new paradigms for spintronic applications. Here, using density functional theory (DFT) calculations, we investigate the spin-dependent electronic transport across vdW magnetic tunnel junctions (MTJs) composed of Fe3GeTe2 ferromagnetic electrodes and a graphene or hexagonal boron nitride (h-BN) spacer layer. For both types of junctions, we find that the junction resistance changes by thousands of percent when the magnetization of the electrodes is switched from parallel to antiparallel. Such a giant tunneling magnetoresistance (TMR) effect is driven by dissimilar electronic structure of the two spin-conducting channels in Fe3GeTe2, resulting in a mismatch between the incoming and outgoing Bloch states in the electrodes and thus suppressed transmission for an

Fatty acid metabolism and steroid biosynthesis are 2 major pathways shared by peroxisomes and mitochondria. Both organelles are in close apposition to the endoplasmic reticulum, with which they communicate via interorganelle membrane contact sites to promote cellular signaling and the exchange of ions and lipids. To date, no convincing evidence of the direct contact between peroxisomes and mitochondria was reported in mammalian cells. Hormone-induced, tightly controlled steroid hormone biosynthesis requires interorganelle interactions. Using immunofluorescent staining and live-cell imaging, we found that dibutyryl-cAMP treatment of MA-10 mouse tumor Leydig cells rapidly induces peroxisomes to approach mitochondria and form peroxisome-mitochondrial contact sites/fusion, revealed by the subcellular distribution of the endogenous acyl-coenzyme A-binding domain (ACBD)2/ECI2 isoform A generated by alternative splicing, and further validated using a proximity ligation assay. This event occurs likely via a peroxisome-like structure, which is mediated by peroxisomal and mitochondrial matrix protein import complexes: peroxisomal import receptor peroxisomal biogenesis factor 5 (PEX5), and the mitochondrial import receptor subunit translocase of outer mitochondrial membrane 20 homolog (yeast) protein. Similar results were obtained using the mLTC-1 mouse tumor Leydig cells. Ectopic expression of the ACBD2/ECI2 isoform A in MA-10 cells led to increased basal and hormone-stimulated steroid formation, indicating that ACBD2/ECI2-mediated peroxisomes-mitochondria interactions favor in the exchange of metabolites and/or macromolecules between these 2 organelles in support of steroid biosynthesis. Considering the widespread occurrence of the ACBD2/ECI2 protein, we propose that this protein might serve as a tool to assist in understanding the contact between peroxisomes and mitochondria.