Author Correction: PAK signalling drives acquired drug resistance to MAPK inhibitors in BRAF-mutant melanomas.

In this Letter, two relevant references were omitted; see the accompanying Amendment for details. The original Letter has not been corrected.

PAK signalling drives acquired drug resistance to MAPK inhibitors in BRAF-mutant melanomas.

Targeted BRAF inhibition (BRAFi) and combined BRAF and MEK inhibition (BRAFi and MEKi) therapies have markedly improved the clinical outcomes of patients with metastatic melanoma. Unfortunately, the efficacy of these treatments is often countered by the acquisition of drug resistance. Here we investigated the molecular mechanisms that underlie acquired resistance to BRAFi and to the combined therapy. Consistent with previous studies, we show that resistance to BRAFi is mediated by ERK pathway reactivation. Resistance to the combined therapy, however, is mediated by mechanisms independent of reactivation of ERK in many resistant cell lines and clinical samples. p21-activated kinases (PAKs) become activated in cells with acquired drug resistance and have a pivotal role in mediating resistance. Our screening, using a reverse-phase protein array, revealed distinct mechanisms by which PAKs mediate resistance to BRAFi and the combined therapy. In BRAFi-resistant cells, PAKs phosphorylate CRAF and MEK to reactivate ERK. In cells that are resistant to the combined therapy, PAKs regulate JNK and ß-catenin phosphorylation and mTOR pathway activation, and inhibit apoptosis, thereby bypassing ERK. Together, our results provide insights into the molecular mechanisms underlying acquired drug resistance to current targeted therapies, and may help to direct novel drug development efforts to overcome acquired drug resistance.

Ahnak scaffolds p11/Anxa2 complex and L-type voltage-gated calcium channel and modulates depressive behavior.

Genetic polymorphisms of the L-type voltage-gated calcium channel (VGCC) are associated with psychiatric disorders including major depressive disorder. Alterations of S100A10 (p11) level are also implicated in the etiology of major depressive disorder. However, the existence of an endogenous regulator in the brain regulating p11, L-type VGCC, and depressive behavior has not been known. Here we report that Ahnak, whose function in the brain has been obscure, stabilizes p11 and Anxa2 proteins in the hippocampus and prefrontal cortex in the rodent brain. Protein levels of Ahnak, p11, and Anxa2 are highly and positively correlated in the brain. Together these data suggest the existence of an Ahnak/p11/Anxa2 protein complex. Ahnak is expressed in p11-positive as well as p11-negative neurons. Ahnak, through its N-terminal region, scaffolds the L-type pore-forming α1 subunit and, through its C-terminal region, scaffolds the ß subunit of VGCC and the p11/Anxa2 complex. Cell surface expression of the α1 subunits and L-type calcium current are significantly reduced in primary cultures of Ahnak knockout (KO) neurons compared to wild-type controls. A decrease in the L-type calcium influx is observed in both glutamatergic neurons and parvalbumin (PV) GABAergic interneurons of Ahnak KO mice. Constitutive Ahnak KO mice or forebrain glutamatergic neuron-selective Ahnak KO mice display a depression-like behavioral phenotype similar to that of constitutive p11 KO mice. In contrast, PV interneuron-selective Ahnak KO mice display an antidepressant-like behavioral phenotype. Our results demonstrate L-type VGCC as an effector of the Ahnak/p11/Anxa2 complex, revealing a novel molecular connection involved in the control of depressive behavior.

Atrazine induces endoplasmic reticulum stress-mediated apoptosis of T lymphocytes via the caspase-8-dependent pathway.

Atrazine (ATR) is one of the most commonly applied broad-spectrum herbicides. Although ATR is well known to be a biologically hazardous molecule with potential toxicity in the immune system, the molecular mechanisms responsible for ATR-induced immunotoxicity remain unclear. In this study, we found that the immunotoxic properties of ATR were mediated through the induction of apoptotic changes in T lymphocytes. Mice exposed to ATR for 4 weeks exhibited a significant decrease in the number of spleen CD3(+) T lymphocytes, while CD19(+) B lymphocytes and nonlymphoid cells were unaffected. ATR exposure also led to inhibition of cell growth and induction of apoptosis in human Jurkat T-cells. Importantly, ATR triggered the activation of caspase-3 and the cleavage of caspase-8 and PARP, whereas it did not affect the release of cytochrome c from the mitochondria in Jurkat T-cells. In addition, ATR activated the unfolded protein response signaling pathway, as indicated by eIF2α phosphorylation and CHOP induction. Our results demonstrate that ATR elicited an immunotoxic effect by inducing ER stress-induced apoptosis in T-cells, therefore providing evidence for the molecular mechanism by which ATR induces dysregulation of the immune system. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 998-1008, 2016.

Evaluating the Validity and Measurement Invariance of the Patient Health Questionnaire-9 Among Canadian Nurses.

Background and Purpose: The patient health questionnaire 9 item (PHQ-9) is a widely used self-reported measure for screening depressive symptoms. This study aims to examine measurement invariance and psychometric properties of the PHQ-9 for screening depressive symptoms in nurses across different nursing roles, gender, and workplace sector. Methods: The study is a secondary analysis of pre-COVID and COVID-19 survey data from 4,176 nurses and 3,238 nurses in British Columbia. Data from the PHQ-9 tested the assumption of unidimensionality, reliability, and presence of differential item functioning (DIF). Results: The PHQ-9 showed excellent internal consistency (r = .9) and a unidimensional factor structure. PHQ-9 items were free of DIF across nursing roles, gender, and workplace sector. Conclusions: This study supported the valid use of the PHQ-9 as a screening tool for depressive symptoms among nurses.

Thirteen years progress: a scoping review of suicide prevention initiatives in post-secondary settings.

Objective: Describe the literature on suicide prevention initiatives (SPIs) in post-secondary settings internationally since 2010. Methods: A scoping review and bibliographic search were conducted across MEDLINE, PsycINFO, CINAHL, and Scopus. Two reviewers independently screened articles and extracted data in consultation with a community social work team. Included articles described SPIs in post-secondary settings. Secondary sources and articles unavailable in English were excluded. Results: After identifying 931 citations, 76 articles representing five continents were included. Included articles spanned 2010 to 2023. Most articles represented North America, used quantitative methods, and focused on gatekeepers. SPIs in post-secondary settings were characterized by standardized and commercially available training programs and a wide variety of 'in-house' initiatives unique to campus communities. Conclusions: The quantity of research on SPIs in post-secondary settings has not kept pace with escalating mental health issues and the extent to which suicide is an urgent public health issue for young adults.

Proteome-wide screening for mitogen-activated protein kinase docking motifs and interactors.

Essential functions of mitogen-activated protein kinases (MAPKs) depend on their capacity to selectively phosphorylate a limited repertoire of substrates. MAPKs harbor a conserved groove located outside of the catalytic cleft that binds to short linear sequence motifs found in substrates and regulators. However, the weak and transient nature of these "docking" interactions poses a challenge to defining MAPK interactomes and associated sequence motifs. Here, we describe a yeast-based genetic screening pipeline to evaluate large collections of MAPK docking sequences in parallel. Using this platform, we analyzed a combinatorial library based on the docking sequences from the MAPK kinases MKK6 and MKK7, defining features critical for binding to the stress-activated MAPKs JNK1 and p38α. Our screen of a library consisting of ~12,000 sequences from the human proteome revealed multiple MAPK-selective interactors, including many that did not conform to previously defined docking motifs. Analysis of p38α/JNK1 exchange mutants identified specific docking groove residues that mediate selective binding. Last, we verified that docking sequences identified in the screen functioned in substrate recruitment in vitro and in cultured cells. Together, these studies establish an approach to characterize MAPK docking sequences and provide a resource for future investigation of signaling downstream of p38 and JNK.

Differential Item Functioning of the Center for Epidemiologic Studies Depression Scale Among Chinese Adolescents.

This study examined differential item functioning (DIF) in the Center for Epidemiologic Studies Depression Scale (CES-D) between Chinese and White adolescents (aged 13 to 17 years) living in Canada. A series of ordinal logistic regressions were used to test for uniform and non-uniform DIF on items in the CES-D. The DIF analyses identified non-uniform DIF for Item 7 ("I felt that everything I did was an effort"). Controlling for gender and strength of ethnic identity in the DIF analyses did not alter the DIF results. The results of this study suggest that CES-D Item 7 does not appear to discriminate at higher levels of depression in Chinese adolescents. The results of this study hold notable implications for the use of the CES-D given that Chinese adolescents demonstrated a systematic difference in expression/experience of depression.

Fecal Microbiota Transplantation for Severe or Fulminant Clostridioides difficile Infection: Systematic Review and Meta-analysis.

BACKGROUND: Severe or fulminant Clostridioides difficile infection (SFCDI) is associated with significant morbidity and mortality. Emerging evidence suggests fecal microbiota transplant (FMT) may be a promising therapy for SFCDI. AIM: This systematic review determines the safety and efficacy of FMT in medically refractory SFCDI. METHODS: A systematic search of the literature was conducted using PubMed (1965 to 2020), Web of Science (1900 to 20), EMBASE (1974 to 2020), and Cochrane Review (1945 to 2020). Quality appraisal by NIH Study Quality Assessment tools, and data extraction were performed by two teams of independent researchers. The primary outcome was resolution of SFCDI 4 weeks after the final FMT. Pooled resolution rates were calculated using generalized linear mixed models estimates. RESULTS: Two hundred and forty patients from 10 studies (8 case series, 1 case-control and 1 randomized study) were included with 209 individual patient-level data. FMT resulted in resolution of SFCDI within 4 weeks in 211/240 individuals for a pooled estimate of 88% (95% confidence interval [CI]: 0.83 to 0.91). The mean number of FMT required was 1.6 for severe and 2.0 for fulminant CDI resolution. The pooled proportional estimates for patients requiring CDI-directed antimicrobials after FMT was 50% (95% CI: 0.06 to 0.94) for severe CDI and 67.0% (95% CI: 0.30 to 0.91) for fulminant CDI. Serious adverse event rates were low. CONCLUSION: FMT appears effective in treating SFCDI patients with low adverse events, but requires multiple treatments with a significant proportion of patients requiring additional anti-CDI antibiotics to achieve resolution. The optimal route of FMT delivery remains unknown. The presence of pseudomembranous colitis may guide additional FMT or anti-CDI antibiotic treatment.

Comprehensive pharmacological profiling of neurofibromatosis cell lines.

Patients with Neurofibromatosis type 1 (NF1) and Neurofibromatosis type 2 (NF2) are predisposed to tumors of the nervous system. NF1 patients predominantly develop neurofibromas, and Malignant Peripheral Nerve Sheath Tumors (MPNST) while NF2 patients develop schwannomas and meningiomas. Here we quantified the drug sensitivities of NF1 and NF2 tumor cell lines in a high throughput platform. The platform contained a comprehensive collection of inhibitors of MEK, RAF, RAS, farnesyl transferase, PAK and ERK, representative drugs against many other cancer pathways including Wnt, Hedgehog, p53, EGF, HDAC, as well as classical cytotoxic agents recommended for treating MPNST, such as doxorubicin and etoposide. We profiled seven NF1-associated MPNST cell lines (ST88-14, ST88-3, 90-8, sNF02.2, T265, S462TY, SNF96.2), one sporadic MPNST cell line (STS26), one schwannoma from a NF2 patient (HEI193), one NF2-deficient malignant meningioma (KT21-MG-Luc5D), one mouse NF2 schwannoma (SC4) and one sporadic rat schwannoma (RT4-67 or RT4). NF1 cells were primarily distinguished from NF2 cells and the sporadic MPNST cell line by their sensitivity to MEK and ERK inhibitors, and to a smaller extent their sensitivity to BH3 mimetics and farnesyl transferase inhibitors. The platform was highly successful in predicting the effects of clinical trials for Neurofibromas.

Cis and trans determinants of epigenetic silencing by Polycomb repressive complex 2 in Arabidopsis.

Disruption of gene silencing by Polycomb protein complexes leads to homeotic transformations and altered developmental-phase identity in plants. Here we define short genomic fragments, known as Polycomb response elements (PREs), that direct Polycomb repressive complex 2 (PRC2) placement at developmental genes regulated by silencing in Arabidopsis thaliana. We identify transcription factor families that bind to these PREs, colocalize with PRC2 on chromatin, physically interact with and recruit PRC2, and are required for PRC2-mediated gene silencing in vivo. Two of the cis sequence motifs enriched in the PREs are cognate binding sites for the identified transcription factors and are necessary and sufficient for PRE activity. Thus PRC2 recruitment in Arabidopsis relies in large part on binding of trans-acting factors to cis-localized DNA sequence motifs.