Na/H exchange regulatory factor-1 (NHERF1) is a PDZ protein that regulates trafficking of several G protein-coupled receptors. The phenotype of NHERF1-null mice suggests that the parathyroid hormone (PTH) receptor (PTH1R) is the principal GPCR interacting with NHERF1. The effect of NHERF1 on receptor recycling is unknown. Here, we characterized NHERF1 effects on PTH1R membrane tethering and recycling by radioligand binding and recovery after maximal receptor endocytosis. Using Chinese hamster ovary cells expressing the PTH1R, where NHERF1 expression could be induced by tetracycline, NHERF1 inhibited PTH1R endocytosis and delayed PTH1R recycling. NHERF1 also inhibited PTH-induced receptor internalization in MC4 osteoblast cells. Reducing constitutive NHERF1 levels in HEK-293 cells with short hairpin RNA directed against NHERF1 augmented PTH1R endocytosis in response to PTH. Mutagenesis of the PDZ-binding domains or deletion of the MERM domain of NHERF1 demonstrated that both are required for inhibition of endocytosis and recycling. Likewise, an intact COOH-terminal PDZ recognition motif in PTH1R is needed. The effect of NHERF1 on receptor internalization and recycling was not associated with altered receptor expression or binding, activation, or phosphorylation but involved ␤-arrestin and dynamin. We conclude that NHERF1 inhibits endocytosis without affecting PTH1R recycling in MC4 and PTH1R-expressing HEK-293 cells. Such an effect may protect against PTH resistance or PTH1R down-regulation in certain cells harboring NHERF1.The magnitude of GPCR 2 -mediated, ligand-induced responses is tightly linked to the balance between signal generation and signal termination. Rapid termination of GPCR signaling is mediated by receptor desensitization and internalization, whereas prolonged reduction in responsiveness is due to down-regulation and diminished receptor biosynthesis. Just as GPCR desensitization provides a mechanism to protect cells against excessive stimulation, GPCR resensitization guards cells against prolonged inactivity and hormone resistance. Sequences located within or at the carboxyl terminus of GPCRs control endocytic sorting and recycling of certain GPCRs (1, 2).Na/H exchange regulatory factor 1 (NHERF1), also known as Ezrin-Radixin-Moesin (ERM)-binding phosphoprotein-50 (EBP50), is a cytoplasmic scaffolding protein implicated in protein targeting and in the assembly of protein complexes (3-6). NHERF1 recruits various GPCRs, ion transporters, and other proteins to the plasma membrane of epithelia and other cells (3,4,7,8).NHERF1 contains two tandem PDZ domains and a MERM domain. Class I PDZ proteins, such as NHERF1, recognize in the target protein the sequence motif (D/E)(S/T)X⌽, where X represents any amino acid and ⌽ is a hydrophobic residue, generally Leu/Ile/Val although it can also be Met (9, 10). As described below, this recognition sequence is present in the parathyroid hormone (PTH) type I receptor (PTH1R). The MERM domain binds to the actin-associated proteins, merlin, ezrin, radixin, and moesi...

USP22 might be an independent predictive factor for CRC prognosis and aberrant expression of USP22 may play an essential role in colorectal carcinogenesis and liver metastasis.

D-limonene is recognized as a potential chemotherapeutic agent, however, the details of this mechanism remain unclear. In this study, we investigated the effects of d-limonene on colon cancer cell viability and its potential mechanism of action in vitro. After 48 h of treatment, d-limonene suppressed the viability of LS174T cells in a dose-dependent manner and caused a dose-dependent apoptotic cell death. D-limonene activated caspase-3 and -9 and PARP cleavage in a dose-dependent manner. Moreover, an increase in Bax protein and cytosol cytochrome c from mitochondria and a decrease in bcl-2 protein were observed following treatment with d-limonene. In addition, d-limonene decreased the levels of p-Akt (Ser473), p-Akt (Thr308) and p-GSK-3β (Ser9), suggesting that d-limonene induced apoptosis via the mitochondrial death pathway and the suppression of the PI3K/Akt pathway.

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High expression of EED, SUZ12 and EZH2 might contribute to the CRC development/progression.