Phosphoinositide 3 kinase enhancer (PIKE) is a recently identified nuclear GTPase that activates nuclear phosphoinositide 3-kinase (PI3 kinase). We have identified, cloned and characterized a new form of PIKE, designated PIKE-L, which, unlike the nuclear PIKE-S, localizes to both the cytoplasm and the nucleus. We demonstrate physiologic binding of PIKE-L to Homer, an adaptor protein known to link metabotropic glutamate receptors to multiple intracellular targets including the inositol 1,4,5-trisphosphate receptor (IP3R). We show that activation of group I metabotropic glutamate receptors (mGluRIs) enhances formation of an mGluRI-Homer-PIKE-L complex, leading to activation of PI3 kinase activity and prevention of neuronal apoptosis. Our findings indicate that this complex mediates the well-known ability of agonists of mGluRI to prevent neuronal apoptosis.

Background Breast cancer is the most common cancer type in female. As microRNAs play vital role in breast cancer, this study aimed to explore the molecular mechanism and clinical value of miR-21 in breast cancer. Methods qRT-PCR was performed to detect miR-21 levels in plasma of 127 healthy controls, 82 benign breast tumor, 252 breast cancer patients, as well as in breast cancer cell lines. Transwell and wound healing assay were used to analyze breast cancer metastasis in response to miR-21 inhibitor. Colony formation and eFluor™ 670 based flow cytometric analysis were used to test breast cancer proliferation following miR-21 inhibitor treatment. Leucine zipper transcription factor-like 1 (LZTFL1), the target gene of miR-21 was predicted by MIRDB, TargetScan 5.1, PicTar and miRanda. Survival analysis of LZTFL1 levels in breast cancer prognosis was estimated with the Kaplan–Meier method by log-rank test according to data from the Cancer Genome Atlas. Luciferase activity assay was performed to confirm the regulation of miR-21 on LZTFL1. LZTFL1 siRNA and miR-21 inhibitor were co-transfected to breast cancer cells, then cell proliferation, migration and epithelial–mesenchymal transition (EMT) makers were tested. BALB/c nude mice were injected in situ with Hs578T cells stably overexpressing miR-21. Breast tumor growth, metastasis and the expression of EMT markers or LZTFL1 were detected in vivo. Results Plasma miR-21 levels were elevated in breast cancer patients compared with healthy controls and benign breast tumor patients, and the miR-21 levels were significantly decreased after surgery comparing with pre operation in 44 patients. Inhibition of miR-21 suppressed cell proliferation and metastasis in breast cancer cells. LZTFL1 was identified as a novel target gene of miR-21. Knockdown of LZTFL1 overcame the suppression of miR-21 inhibitor on cell proliferation, metastasis and the expression of EMT markers in breast cancer cells. miR-21 overexpression promoted breast cancer cell proliferation and metastasis in vivo. Conclusions These results indicate that plasma miR-21 level is a crucial biomarker for breast cancer diagnosis and targeting miR-21–LZTFL1–EMT axis might be a promising strategy in breast cancer therapy. Trial registration Retrospectively registered. Electronic supplementary material The online version of this article (10.1186/s12885-019-5951-3) contains supplementary material, which is available to authorized users.

No abstract

Group I metabotropic glutamate receptors (mGluRs), including mGluR1 and mGluR5, are G protein–coupled receptors (GPCRs) that are expressed at excitatory synapses in brain and spinal cord. GPCRs are often negatively regulated by specific G protein–coupled receptor kinases and subsequent binding of arrestin-like molecules. Here we demonstrate an alternative mechanism in which group I mGluRs are negatively regulated by proline-directed kinases that phosphorylate the binding site for the adaptor protein Homer, and thereby enhance mGluR–Homer binding to reduce signaling. This mechanism is dependent on a multidomain scaffolding protein, Preso1, that binds mGluR, Homer and proline-directed kinases and that is required for their phosphorylation of mGluR at the Homer binding site. Genetic ablation of Preso1 prevents dynamic phosphorylation of mGluR5, and Preso1−/− mice exhibit sustained, mGluR5-dependent inflammatory pain that is linked to enhanced mGluR signaling. Preso1 creates a microdomain for proline-directed kinases with broad substrate specificity to phosphorylate mGluR and to mediate negative regulation.

Homer proteins are adapters that physically bind and functionally couple target proteins (1, 2). Homer1, Homer2, and Homer3 are encoded by three mammalian genes whose expression is dynamically regulated by cellular activity (2) and can attain high levels of protein in the nervous system where their functional regulation of excitatory signaling has been studied (3-5). A common element of structure of all Homer proteins is an N-terminal Enabled/Vasp homology domain (EVH1) essential for binding Homer ligands (6 -7). Crystallographic analysis of the EVH1 domain binding surface has revealed its specific association with polyproline ligands (7) that have previously been defined within plasmalemmal glutamate receptors including mGluR1a 1 and mGluR5a/b (1), inositol 1,4,5-trisphosphate receptors (IP 3 R) localized within endoplasmic and sarcoplasmic reticulum (SR) membranes (1), and cytoplasmic Shank proteins that are part of the N-methyl-D-aspartate receptor-associated PSD-95 complex (8, 9). A C-terminal coiled-coil domain is responsible for Homer self-multimerization (10 -13). Although full-length Homer proteins are constitutively expressed in a number of tissues, immediate-early gene products of the Homer1 gene including Homer1a and Ania 3 lack the CC domain (3, 10). "Short form" Homer1a is rapidly and transiently induced by physiological synaptic stimuli that evoke long term potentiation in the hippocampus (3, 10) or in striatum by the addition of dopaminergic drugs (3). Thus, a use-dependent exchange of multimeric and protomeric short forms of Homer appears to be responsible for dynamic regulation of context-dependent signaling in neurons. The functional influences of Homer adaptors on targeted protein have not been identified. Multi-PDZ domain proteins have been reported to cluster membrane ion channels with the result that the channel become active, but this effect is mimicked by agents that otherwise cross-link the channel (14). Homer binding to mGluR1 was recently reported to define agonist-independent activity of the receptor (15); however, this report did not define a molecular mechanism. The direct consequence of forming Homer-IP 3 R complexes on the dynamics of endoplasmic reticulum/SR Ca 2ϩ release and its possible contribution to temporal and spatial aspects of Ca 2ϩ signals remain unclear.Recently all three Homer mRNAs have also been detected in striated muscle, and Homer protein has been identified within skeletal and cardiac muscle (4, 5). Moreover, putative Homer ligand sequences are found within both the type 1 ryanodine receptor (RyR1) and the ␣ 1S -subunit of the dihydropyridine receptor (DHPR; CACNA1S) of skeletal muscle (7). RyR1 assembles as tetrameric structures within junctional regions of SR where it forms large organized arrays (16). RyR1 forms physical associations with ␣ 1S -DHPR that are essential for engaging reciprocal signaling units that are essential for excitation-contraction (E-C) coupling, a process whereby depolarization in the T-tubules triggers Ca 2ϩ release from SR resulting i...

Circular RNAs (circRNA), a class of noncoding RNAs, have been found to be involved in various diseases. Here, the expression levels of the circRNA hsa_circ_0001445 in 73 pairs of hepatocellular carcinoma (HCC) and adjacent nontumor tissues were investigated by quantitative real-time polymerase chain reaction (qRT-PCR). Our data demonstrate that the hsa_circ_0001445 levels were significantly decreased in HCC tissues (P < 0.001) and markedly associated with the number of tumor foci (P = 0.014). Furthermore, in vitro approaches showed that overexpression of hsa_circ_0001445 promoted apoptosis and inhibited proliferation, migration, and invasion of HCC-derived cells, suggesting that hsa_circ_0001445 might be involved in the development of HCC. In addition, we found that the plasma hsa_circ_0001445 transcription levels in HCC patients were lower than those in cirrhosis (P < 0.001) and hepatitis B (P < 0.001) patients as well as in healthy controls (P < 0.001). In fact, receiver operating characteristic curve analysis indicated that plasma hsa_circ_0001445 could be a fairly accurate marker to distinguish HCC cases from healthy controls as well as patients with cirrhosis or hepatitis B.

LncRNAs play critical roles in gastric cancer (GC). In this study, the expression of fourteen cancer related lncRNAs were investigated in paired tissues of 66 patients with GC, Realtime RT-PCR revealed that ZFAS1 was significantly upregulated. We then examined the expression of ZFAS1 in plasmas derived from 77 GC patients before- and post-operations and 60 healthy individuals, and found that circulating ZFAS1 was also upregulated in GC patients and operation can reduce its presence in plasma. To investigate the potential mechanisms, we compared the expression of ZFAS1 in multiple gastric cell lines and one normal cell line and found that ZFAS1 was up-regulated in GC cell lines. Furthermore, circulating tumor cells (CTC) were simulated by mixing GC cells with peripheral blood. After EpCAM antibody-based cell sorting, we found that the expression of ZFAS1 was positively correlated with EMT property of CTCs. In GC patient tissue samples, we found that Twist was positively correlated with ZFAS1 by immunohistochemical staining. Taken together, our results suggested that ZFAS1 was up-regulated in both tissues and plasmas of GC patients, and may be involved in regulation of EMT in GC progression. Thus, ZFAS1 might serve as a potential diagnostic marker and/or therapeutic target for GC.

No abstract