Human calcium-sensing receptor (CaSR) is a G-protein-coupled receptor (GPCR) that maintains extracellular Ca2+ homeostasis through the regulation of parathyroid hormone secretion. It functions as a disulfide-tethered homodimer composed of three main domains, the Venus Flytrap module, cysteine-rich domain, and seven-helix transmembrane region. Here, we present the crystal structures of the entire extracellular domain of CaSR in the resting and active conformations. We provide direct evidence that L-amino acids are agonists of the receptor. In the active structure, L-Trp occupies the orthosteric agonist-binding site at the interdomain cleft and is primarily responsible for inducing extracellular domain closure to initiate receptor activation. Our structures reveal multiple binding sites for Ca2+ and PO43- ions. Both ions are crucial for structural integrity of the receptor. While Ca2+ ions stabilize the active state, PO43- ions reinforce the inactive conformation. The activation mechanism of CaSR involves the formation of a novel dimer interface between subunits.DOI: http://dx.doi.org/10.7554/eLife.13662.001

Macrophages are prominent immune cells in the tumor microenvironment that exert potent effects on cancer metastasis. However, the signals and receivers for the tumor-macrophage communication remain enigmatic. Here, we show that G protein-coupled receptor 132 (Gpr132) functions as a key macrophage sensor of the rising lactate in the acidic tumor milieu to mediate the reciprocal interaction between cancer cells and macrophages during breast cancer metastasis. Lactate activates macrophage Gpr132 to promote the alternatively activated macrophage (M2)-like phenotype, which, in turn, facilitates cancer cell adhesion, migration, and invasion. Consequently, Gpr132 deletion reduces M2 macrophages and impedes breast cancer lung metastasis in mice. Clinically, Gpr132 expression positively correlates with M2 macrophages, metastasis, and poor prognosis in patients with breast cancer. These findings uncover the lactate-Gpr132 axis as a driver of breast cancer metastasis by stimulating tumor-macrophage interplay, and reveal potential new therapeutic targets for breast cancer treatment.reast cancer is the most frequently diagnosed nonskin type of malignancy, and the second leading cause of cancer-related death in women. The 5-y survival rate is 89% in patients who have primary breast cancer, whereas the medium survival of patients with metastatic breast cancer is only 1-2 y (1, 2). Metastasis is the primary cause of breast cancer-related deaths; however, the molecular mechanisms underlying this process are still poorly understood. It has been well established that the tumor microenvironment plays an important role in breast cancer metastasis (3-6). Tumor-associated macrophages (TAMs) make up the largest population of stromal cells that suppress antitumor immunity and foster tumor progression in mouse models of breast cancer (3,(6)(7)(8). TAMs also promote metastasis and correlate with poor prognosis in patients with breast cancer (7, 9). Conversely, TAM functions are also tightly regulated by tumor cells (10, 11). However, the mechanisms underlying this reciprocal regulation between cancer cells and macrophages during metastasis remain elusive.Macrophages are heterogeneous immune cells that can exhibit distinct functions and phenotypes depending on different microenvironment signals (9, 12). They can be broadly divided into classically activated (M1) and alternatively activated (M2) macrophages, the latter of which generally display promalignancy activity (9, 12). In solid tumors, TAMs are usually biased toward M2 (9). Due to hypoxia and glycolytic cancer cell metabolism, the tumor environment is usually acidic, which affects tumor progression by acting on both cancer cells and stromal cells, including macrophages (10,13,14). A recent study shows that cancer cell-derived lactate can educate macrophages to functional TAMs, which, in turn, promotes tumor growth (14). Nonetheless, how lactate activation of TAMs affects cancer metastasis is poorly understood. Importantly, the molecular basis by which macrophages sense and respond t...

SUMMARYNG2-expressing cells (NG2 cells or polydendrocytes) generate oligodendrocytes throughout the CNS and a subpopulation of protoplasmic astrocytes in the gray matter of the ventral forebrain. The mechanisms that regulate their oligodendrocyte or astrocyte fate and the degree to which they exhibit lineage plasticity in vivo have remained unclear. The basic helix-loop-helix transcription factor Olig2 is required for oligodendrocyte specification and differentiation. We have found that Olig2 expression is spontaneously downregulated in NG2 cells in the normal embryonic ventral forebrain as they differentiate into astrocytes. To further examine the role of Olig2 in NG2 cell fate determination, we used genetic fate mapping of NG2 cells in constitutive and tamoxifen-inducible Olig2 conditional knockout mice in which Olig2 was deleted specifically in NG2 cells. Constitutive deletion of Olig2 in NG2 cells in the neocortex and corpus callosum but not in ventral forebrain caused them to convert their fate into astrocytes, with a concomitant severe reduction in the number of oligodendrocytes and myelin. Deletion of Olig2 in NG2 cells in perinatal mice also resulted in astrocyte generation from neocortical NG2 cells. These observations indicate that the developmental fate of NG2 cells can be switched by altering a single transcription factor Olig2.

Highlights d Oncogenic BRD4-S and tumor-suppressive BRD4-L in breast cancer d Inducible BRD4-L/S transgenic mice exhibiting opposing functions of BRD4 isoforms d Genome-wide RNA-seq, ChIP-seq, and CUT&RUN profiling of BRD4-S and BRD4-L d EN1/BRD4-S-coregulated enhancer modulating the matrisome ECM network

Human GABA B G protein-coupled receptor (GPCR), a member of the class C family, mediates inhibitory neurotransmission and is implicated in epilepsy, pain, and addiction 1 . A unique GPCR known to require heterodimerization for function 2 – 6 , its two subunits, GABA B1 and GABA B2 , are structurally homologous but perform distinct and complementary functions. GABA B1 recognizes orthosteric ligand 7 , 8 , while GABA B2 couples with G protein 9 – 14 . Each subunit is characterized by an extracellular Venus flytrap (VFT) module, a descending peptide linker, a seven-helix transmembrane (TM) domain, and a cytoplasmic tail 15 . Whereas the VFT heterodimer structure has been resolved 16 , the structure of the full-length receptor and its transmembrane signaling mechanism remain unknown. Here we present a near full-length structure of the GABA B receptor, captured in an inactive state via cryo-electron microscopy (EM). Our structure reveals multiple ligands pre-associated with the receptor, including two large endogenous phospholipids embedded within the TM domains to maintain receptor integrity and modulate receptor function. We also identify a novel heterodimer interface between TM helices 5 and 3 of both subunits, which serves as a signature of the inactive conformation. A unique ′intersubunit latch′ within this TM interface maintains the inactive state, and its disruption leads to constitutive receptor activity.