The C-terminal Amphipathic Helix of Carboxypeptidase E Mediates Export from the ER and Secretion via Lysosomes.

Carboxypeptidase E (CPE), an essential enzyme in the biosynthetic production line of most peptide hormones and neuropeptides, is predominantly expressed in endocrine tissues and in the nervous system. CPE is active in acidic environments where it cleaves the C'-terminal basic residues of peptide precursors to generate their bioactive form. Consequently, this highly conserved enzyme regulates numerous fundamental biological processes. Here, we combined live-cell microscopy and molecular analysis to examine the intracellular distribution and secretion dynamics of fluorescently tagged CPE. We show that, in non-endocrine cells, tagged-CPE is a soluble luminal protein that is efficiently exported from the ER via the Golgi apparatus to lysosomes. The C'-terminal conserved amphipathic helix serves as a lysosomal and secretory granule targeting and a secretion motif. Following secretion, CPE may be reinternalized into the lysosomes of neighboring cells.

Anxiolytic and antidepressants' effect of Crataegus pinnatifida (Shan Zha): biochemical mechanisms.

Depression and anxiety disorders are highly prevalent. Selective serotonin reuptake inhibitors (SSRIs) are the current first-line treatment for depression, but they have pronounced limitations. Traditional Chinese medicine can serve as a safe and effective alternative to conventional drugs, particularly since many herbal remedies have already been approved for human use as food additives, making the transition from bench to bedside more efficient. We previously demonstrated that a novel herbal treatment (NHT) induces anxiolytic- and antidepressant-like effects. NHT consists of four herbs: Crataegus pinnatifida (Shan Zha), Triticum aestivum (Fu Xiao Mai), Lilium brownii (Baihe), and the fruit of Ziziphus jujuba (Da Zao). In the current study, we examined the antidepressant-like and anxiolytic-like activities of each individual herb on stressed mice and compared those to the effects of NHT and escitalopram. We show here that Shan Zha is sufficient to produce an anxiolytic and antidepressant-like effect similar to NHT or the escitalopram through activation of 5-HT1A receptor and an elevation in BDNF levels in the hippocampus and Pre-frontal cortex (PFC). Chronic treatment with Shan Zha did not alter serotonin transporter levels in the PFC, as opposed to escitalopram treatment. These results were confirmed in vitro, as none of the herbs blocked SERT activity in Xenopus oocytes. Notably, Shan Zha is sold as a nutritional supplement; thus, its transition to clinical trials can be easier. Once its efficacy and safety are substantiated, Shan Zha may serve as an alternative to conventional antidepressants.

A genome-wide CRISPR activation screen reveals Hexokinase 1 as a critical factor in promoting resistance to multi-kinase inhibitors in hepatocellular carcinoma cells.

Hepatocellular carcinoma (HCC) is often diagnosed at an advanced stage and is, therefore, treated with systemic drugs, such as tyrosine-kinase inhibitors (TKIs). These drugs, however, offer only modest survival benefits due to the rapid development of drug resistance. To identify genes implicated in TKI resistance, a cluster of regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 activation screen was performed in hepatoma cells treated with regorafenib, a TKI used as second-line therapy for advanced HCC. The screen results show that Hexokinase 1 (HK1), catalyzing the first step in glucose metabolism, is a top candidate for conferring TKI resistance. Compatible with this, HK1 was upregulated in regorafenib-resistant cells. Using several experimental approaches, both in vitro and in vivo, we show that TKI resistance correlates with HK1 expression. Furthermore, an HK inhibitor resensitized resistant cells to TKI treatment. Together, our data indicate that HK1 may function as a critical factor modulating TKI resistance in hepatoma cells and, therefore, may serve as a biomarker for treatment success.

A CRISPR knockout screen reveals new regulators of canonical Wnt signaling.

The Wnt signaling pathways play fundamental roles during both development and adult homeostasis. Aberrant activation of the canonical Wnt signal transduction pathway is involved in many diseases including cancer, and is especially implicated in the development and progression of colorectal cancer. Although extensively studied, new genes, mechanisms and regulatory modulators involved in Wnt signaling activation or silencing are still being discovered. Here we applied a genome-scale CRISPR-Cas9 knockout (KO) screen based on Wnt signaling induced cell survival to reveal new inhibitors of the oncogenic, canonical Wnt pathway. We have identified several potential Wnt signaling inhibitors and have characterized the effects of the initiation factor DExH-box protein 29 (DHX29) on the Wnt cascade. We show that KO of DHX29 activates the Wnt pathway leading to upregulation of the Wnt target gene cyclin-D1, while overexpression of DHX29 inhibits the pathway. Together, our data indicate that DHX29 may function as a new canonical Wnt signaling tumor suppressor and demonstrates that this screening approach can be used as a strategy for rapid identification of novel Wnt signaling modulators.