Coupling of mGluR/Homer and PSD-95 complexes by the Shank family of postsynaptic density proteins

Shank is a recently described family of postsynaptic proteins that function as part of the NMDA receptor-associated PSD-95 complex (Naisbitt et al., 1999 [this issue of Neuron]). Here, we report that Shank proteins also bind to Homer. Homer proteins form multivalent complexes that bind proline-rich motifs in group 1 metabotropic glutamate receptors and inositol trisphosphate receptors, thereby coupling these receptors in a signaling complex. A single Homer-binding site is identified in Shank, and Shank and Homer coimmunoprecipitate from brain and colocalize at postsynaptic densities. Moreover, Shank clusters mGluR5 in heterologous cells in the presence of Homer and mediates the coclustering of Homer with PSD-95/GKAP. Thus, Shank may cross-link Homer and PSD-95 complexes in the PSD and play a role in the signaling mechanisms of both mGluRs and NMDA receptors.

Homer regulates the association of group 1 metabotropic glutamate receptors with multivalent complexes of homer-related, synaptic proteins

Homer is a neuronal immediate early gene (IEG) that is enriched at excitatory synapses and binds group 1 metabotropic glutamate receptors (mGluRs). Here, we characterize a family of Homer-related proteins derived from three distinct genes. Like Homer IEG (now termed Homer 1a), all new members bind group 1 mGluRs. In contrast to Homer 1a, new members are constitutively expressed and encode a C-terminal coiled-coil (CC) domain that mediates self-multimerization. CC-Homers form natural complexes that cross-link mGluRs and are enriched at the postsynaptic density. Homer 1a does not multimerize and blocks the association of mGluRs with CC-Homer complexes. These observations support a model in which the dynamic expression of Homer 1a competes with constitutively expressed CC-Homers to modify synaptic mGluR properties.

Protein topology of presenilin 1

Mutations in a gene encoding a multitransmembrane protein, termed presenilin 1 (PS1), are causative in the majority of early-onset cases of AD. To determine the topology of PS1, we utilized two strategies: first, we tested whether putative transmembranes are sufficient to export a protease-sensitive substrate across a lipid bilayer; and second, we examined the binding of antibodies to specific PS1 epitopes in cultured cells selectively permeabilized with the pore-forming toxin, streptolysin-O. We document that the "loop," N-terminal, and C-terminal domains of PS1 are oriented toward the cytoplasm.

The tumor suppressor PTEN is exported in exosomes and has phosphatase activity in recipient cells

Exosomes are microvesicles of endosomal origin that are secreted, and their contents (proteins, lipids, DNA, or microRNAs) can alter the physiological states of recipient cells. We demonstrated that phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a tumor suppressor protein normally localized in the cytoplasm and nucleus, was secreted in exosomes. Secreted PTEN was internalized by recipient cells with resultant functional activity, which resulted in reduced phosphorylation of the serine and threonine kinase Akt and reduced cellular proliferation. PTEN secretion in exosomes required Ndfip1, an adaptor protein for members of the Nedd4 family of E3 ubiquitin ligases. Without Ndfip1, neither Nedd4-1 nor Nedd4-2 promoted the recruitment of PTEN into exosomes. In addition, lysine 13 within PTEN, which is required for its ubiquitination by Nedd4-1, was required for exosomal transport of PTEN. These results implicate Ndfip1 as a molecular regulator of the exosomal export of PTEN, with consequences for non-cell-autonomous PTEN activity. Thus, we suggest that the ability of PTEN to exert phosphatase activity beyond the cell in which it is produced has implications for PTEN function during development, health, and disease.

Presynaptic clustering of mGluR7a requires the PICK1 PDZ domain binding site

Aggregation of neurotransmitter receptors at pre- and postsynaptic structures is crucial for efficient neuronal communication. In contrast to the wealth of information about postsynaptic specializations, little is known about the molecular organization of presynaptic membrane proteins. We show here that the metabotropic glutamate receptor mGluR7a, which localizes specifically to presynaptic active zones, interacts in vitro and in vivo with PICK1. Coexpression in heterologous systems induces coclustering dependent upon the extreme C terminus of mGluR7a and the PDZ domain of PICK1. mGluR7a and PICK1 localize to excitatory synapses in hippocampal neurons. Furthermore, whereas transfected mGluR7a clusters at presynaptic sites, mGluR7adelta3 lacking the PICK1 binding site targets to axons but does not cluster. These results suggest that PICK1 is a component of the presynaptic machinery involved in mGluR7a aggregation and in modulation of glutamate neurotransmission.

Immunocytochemical investigation of luteinizing hormone-releasing hormone neurons in Syrian hamsters maintained under long or short days

Light-microscope immunocytochemistry was used to investigate the LHRH system of adult male Syrian hamsters. Half of the animals were transferred from long to short photoperiods (14L:10D to 6L:18D) for 10 wk, causing plasma gonadotropin levels and the testes to revert to a prepubertal condition. In spite of the marked differences in the reproductive axis between the two groups of hamsters, the number of immunopositive LHRH neurons observed in the preoptic-medial septal area and diagonal band of Broca was approximately 400 in both cases; of these, 87-91% were monopolar and 9-13% were bipolar, regardless of whether the brains were sectioned in a coronal or sagittal plane. These results, therefore, fail to support the hypothesis that photoperiodic changes in the number of LHRH neurons play a major role in controlling the seasonal regression and recrudescence of the reproductive system in the hamster. However, morphometric analysis of the perikarya using an IBAS 2000 automatic image analyzer revealed a photoperiod-related difference. Surprisingly, the perikarya of both monopolar and bipolar LHRH neurons were significantly larger in hamsters that had been maintained on short days, as opposed to long days. These findings, therefore, are in harmony with the view that the inhibitory effect of short days on the reproductive axis is mediated through a suppression of LHRH secretion, which in turn is reflected as an increase in the net content of LHRH within the brain.

Genome-scale CRISPR-Cas9 screen of Wnt/β-catenin signaling identifies therapeutic targets for colorectal cancer

Aberrant activation of Wnt/β-catenin pathway is a key driver of colorectal cancer (CRC) growth and of great therapeutic importance. In this study, we performed comprehensive CRISPR screens to interrogate the regulatory network of Wnt/β-catenin signaling in CRC cells. We found marked discrepancies between the artificial TOP reporter activity and β-catenin-mediated endogenous transcription and redundant roles of T cell factor/lymphoid enhancer factor transcription factors in transducing β-catenin signaling. Compiled functional genomic screens and network analysis revealed unique epigenetic regulators of β-catenin transcriptional output, including the histone lysine methyltransferase 2A oncoprotein (KMT2A/Mll1). Using an integrative epigenomic and transcriptional profiling approach, we show that KMT2A loss diminishes the binding of β-catenin to consensus DNA motifs and the transcription of β-catenin targets in CRC. These results suggest that KMT2A may be a promising target for CRCs and highlight the broader potential for exploiting epigenetic modulation as a therapeutic strategy for β-catenin-driven malignancies.

Generation and multi-dimensional profiling of a childhood cancer cell line atlas defines new therapeutic opportunities

Pediatric solid and central nervous system tumors are the leading cause of cancer-related death among children. Identifying new targeted therapies necessitates the use of pediatric cancer models that faithfully recapitulate the patient's disease. However, the generation and characterization of pediatric cancer models has significantly lagged behind adult cancers, underscoring the urgent need to develop pediatric-focused cell line resources. Herein, we establish a single-site collection of 261 cell lines, including 224 pediatric cell lines representing 18 distinct extracranial and brain childhood tumor types. We subjected 182 cell lines to multi-omics analyses (DNA sequencing, RNA sequencing, DNA methylation), and in parallel performed pharmacological and genetic CRISPR-Cas9 loss-of-function screens to identify pediatric-specific treatment opportunities and biomarkers. Our work provides insight into specific pathway vulnerabilities in molecularly defined pediatric tumor classes and uncovers biomarker-linked therapeutic opportunities of clinical relevance. Cell line data and resources are provided in an open access portal.

Diurnal expression of Fos in luteinizing hormone-releasing hormone neurons of Syrian hamsters

The aim of the present study was two-fold: first, to examine the temporal relationship between increased expression of Fos in LHRH neurons of proestrous hamsters and increased plasma levels of LH, FSH, estradiol-17 beta (E2), and progesterone (P4); and second, to establish whether male hamsters, like females, also show diurnal variations in the number of LHRH neurons expressing Fos. Blood samples were collected from proestrous females at 0900 n, 1200 h, 1500 h, and 1800 h and also from males at 0300 h, 0900 h, 1500 h, and 2100 h. RIA of the plasma revealed significant peaks of LH, FSH, and E2 at 1500 h, and of P4 at 1800 h in the females; a significant but smaller peak of LH also occurred at 1500 h in the males. Double-label immunocytochemistry, using antibodies directed against amino acids 127-152 of the human Fos protein and against LHRH, showed that female hamsters expressed Fos in fewer than 10% of their LHRH neurons during the morning and at noon of proestrus but in approximately 41% of these neurons during the late afternoon (1800 h). In contrast, no expression of Fos occurred in LHRH neurons of male hamsters at any time of the day. The finding that the females showed an increase in the number of LHRH neurons expressing Fos after, and not before, the initiation of the preovulatory gonadotropin surge is significant because it does not readily support the hypothesis that this expression of immediate-early genes is in some way associated with the induction of the surge. Instead, the results are consistent with the view that expression of Fos in LHRH neurons reflects either the activation of a mechanism responsible for terminating the surge or, alternatively, the activation of a compensatory mechanism responsible for replenishing depleted neuropeptide stocks.

Maturation of the hypothalamo-pituitary-gonadal axis of male Syrian hamsters

Light-microscope immunocytochemistry (ICC) was used to investigate postnatal changes in the morphology of LHRH neurons in the brains of male Syrian hamsters and to relate these changes to more overt maturational developments within the hypothalamo-pituitary-gonadal axis. The animals were maintained under long-day photoperiods (14L:10D), and groups of 6-7 were killed at 10-day intervals from Day 15 to Day 65. Their brains were fixed with 4% paraformaldehyde, sectioned sagittally with a vibratome (75 microns), and processed for ICC using monoclonal LHRH antibody HU4H. Throughout the study period, the hamsters showed a progressive increase in plasma gonadotropin levels, closely followed by an increase in testicular weight and plasma testosterone levels. Histology of the testes revealed that spermatogenesis was already qualitatively completed by Day 35 and quantitative aspects were established by Day 45. Within the brain, LHRH neuronal perikarya were distributed primarily in the medial septal-preoptic area and the diagonal band of Broca; morphologically, these immunopositive neurons were either monopolar or bipolar. The total number of LHRH neurons detected in the areas examined was approximately 440 throughout the developmental period, and the relative proportions of monopolar and bipolar subtypes (86% and 14%, respectively) remained unchanged. In contrast, the area of the perikarya, as determined by autoimage analysis, showed a highly significant age-related increase, both for the monopolar and bipolar neurons. It is suggested that these developmental changes in the LHRH neurons reflect an increase in LHRH synthesis and may, therefore, provide a neuroendocrine trigger for the onset of puberty.

MED12 and BRD4 cooperate to sustain cancer growth upon loss of mediator kinase

Mediator kinases (CDK8/19) are transcriptional regulators broadly implicated in cancer. Despite their central role in fine-tuning gene-expression programs, we find complete loss of CDK8/19 is tolerated in colorectal cancer (CRC) cells. Using orthogonal functional genomic and pharmacological screens, we identify BET protein inhibition as a distinct vulnerability in CDK8/19-depleted cells. Combined CDK8/19 and BET inhibition led to synergistic growth retardation in human and mouse models of CRC. Strikingly, depletion of CDK8/19 in these cells led to global repression of RNA polymerase II (Pol II) promoter occupancy and transcription. Concurrently, loss of Mediator kinase led to a profound increase in MED12 and BRD4 co-occupancy at enhancer elements and increased dependence on BET proteins for the transcriptional output of cell-essential genes. In total, this work demonstrates a synthetic lethal interaction between Mediator kinase and BET proteins and exposes a therapeutic vulnerability that can be targeted using combination therapies.

Ndfip1 represses cell proliferation by controlling Pten localization and signaling specificity

Pten controls a signaling axis that is implicated to regulate cell proliferation, growth, survival, migration, and metabolism. The molecular mechanisms underlying the specificity of Pten responses to such diverse cellular functions are currently poorly understood. Here we report the control of Pten activity and signaling specificity during the cell cycle by Ndfip1 regulation of Pten spatial distribution. Genetic deletion of Ndfip1 resulted in a loss of Pten nuclear compartmentalization and increased cell proliferation, despite cytoplasmic Pten remaining active in regulating PI3K/Akt signaling. Cells lacking nuclear Pten were found to have dysregulated levels of Plk1 and cyclin D1 that could drive cell proliferation. In vivo, transgene expression of Ndfip1 in the developing brain increased nuclear Pten and lengthened the cell cycle of neuronal progenitors, resulting in microencephaly. Our results show that local partitioning of Pten from the cytoplasm to the nucleus represents a key mechanism contributing to the specificity of Pten signaling during cell proliferation.

Reproducibility of computer-assisted joint alignment measurement in OA knee radiographs

OBJECTIVES

(1) To investigate the reproducibility of computer-assisted measurements of knee alignment angle (KA) from digitized radiographs of osteoarthritis (OA) participants requiring total knee arthroplasty (TKA) and (2) to determine whether landmark choice affects the precision of KA measurements on radiographs.

METHODS

Using a custom algorithm, femoral, central, and tibial measurement-guiding rules were interactively placed on digitized posteroanterior fixed-flexion knee radiographs by mouse control and positioned according to different anatomic landmarks. The angle subtended by lines connecting these guiding rules was measured by three readers to assess interobserver, intraobserver and experience-inexperience reproducibility. Test-retest reproducibility was evaluated with duplicate radiographs from a healthy cohort. Reproducibility was assessed using root-mean square coefficients of variation (RMSCV%). The Bland-Altman method was performed on data obtained from varying anatomic landmarks (confidence interval, CI= 95%).

RESULTS

From 16 healthy and 30 TKA participants, reproducibility analyses revealed a high degree of intraobserver (n=38, RMSCV=0.56%), interobserver (n=38, RMSCV=0.72%), test-retest (n=16, RMSCV=0.87%) and experience-inexperience (n=38, RMSCV=0.73%) reproducibility with variances below 1%. Varying the orientation of tibial and femoral rules according to anatomic landmarks produced a difference that exceeded an a priori limit of agreement of -1.11 degrees to +1.67 degrees.

CONCLUSION

Our custom-designed software provides a robust method for measuring KAs within digitized knee radiographs. Although test-retest analyses were only performed in a healthy cohort, we anticipate a similar degree of reproducibility in an OA sample. A standardized set of anatomic landmarks employed for KA measurement is recommended since arbitrary selection of landmarks resulted in imprecise KA measurement even with a computer-assisted technique.

Elimination of Cancer Health Disparities through the Acceleration of HPV Vaccines and Vaccinations: A Simplified Version of the President's Cancer Panel Report on HPV Vaccinations

The human papillomavirus (HPV) is a major public health concern affecting both females and males. HPV is associated with cervical, anal, head and neck cancers. About 99% of all cervical cancers are related to HPV. HPV vaccines, Gardasil, Cervarix, and Gardasil 9 are used in the primary prevention of HPV related cancers. Gardasil and Gardasil 9 are available for use in both females and males ages 9 to 26, while Cervarix is available for females ages 9 to 25. Gardasil 9 was approved by the FDA for prevention against additional HPV types. Despite the availability of this preventative measure against cervical cancer, the rate of HPV vaccination in the United States remains lower than that of other industrialized nations. The purpose of this study is to elucidate mechanisms to help increase the HPV vaccination rate by using education as a tool; by simplifying the president report so that lay person can understand the information presented in the report. Through the quantitative examination of the data from the states with the lowest and highest vaccination rates, using SPSS statistical analysis; we analyzed several factors involved with the low uptake of the vaccines. The results collected show that socioeconomic status, misconceptions about HPV, and misconceptions about the safety of the vaccines were identified as possible obstacles to the effective uptake of HPV vaccinations. The proposals made by the President's Cancer Panel to accelerate the uptake of vaccines include, increasing coverage of the vaccines through government-sponsored programs, and the Affordable Care Act; increasing accessibility to vaccines through pharmacies, schools, and clinics; and disseminating more information on HPV to healthcare providers, parents, caregivers, and patients. Allowing greater accessibility to the vaccines for all populations regardless of income, education, and eliminating misconceptions of the vaccines would play a significant role in eliminating cancer.

Decision-theoretic refinement planning in medical decision making: management of acute deep venous thrombosis

Decision-theoretic refinement planning is a new technique for finding optimal courses of action. The authors sought to determine whether this technique could identify optimal strategies for medical diagnosis and therapy. An existing model of acute deep venous thrombosis of the lower extremities was encoded for analysis by the decision-theoretic refinement planning system (DRIPS). The encoding represented 6,206 possible plans. The DRIPS planner used artificial intelligence techniques to eliminate 5,150 plans (83%) from consideration without examining them explicitly. The DRIPS system identified the five strategies that minimized cost and mortality. The authors conclude that decision-theoretic planning is useful for examining large medical-decision problems.

[Diagnose importance of multiparametric magnetic resonance tomography for prostate cancer]

Prostate cancer is biologically and clinically a heterogeneous disease which makes imaging evaluation challenging. Magnetic resonance imaging (MRI) has considerable potential to improve prostate cancer detection and characterization. Until recently morphologic MRI has not been routinely incorporated into clinical care because of its limitation to detect, localize and characterize prostate cancer. Performing prostate gland MRI using functional techniques has the potential to provide unique information regarding tumor behavior, including treatment response. In order for multiparametric MRI data to have an impact on patient management, the collected data need to be relayed to clinicians in a standardized way for image construction, analysis and interpretation. This will ensure that patients are treated effectively and in the most appropriate way. Scoring systems similar to those employed successfully for breast imaging need to be developed.

Pyrazinamide-induced hyperuricemia

Elevated uric acid levels can cause crystal deposition and may lead to gout, urolithiasis, and urate nephropathy. The authors report on the case of a 34-year-old male whose hyperuricemia was associated with the antituberculous drug pyrazinamide.

Decision-theoretic refinement planning: a new method for clinical decision analysis

Clinical decision analysis seeks to identify the optimal management strategy by modelling the uncertainty and risks entailed in the diagnosis, natural history, and treatment of a particular problem or disorder. Decision trees are the most frequently used model in clinical decision analysis, but can be tedious to construct, cumbersome to use, and computationally prohibitive, especially with large, complex decision problems. We present a new method for clinical decision analysis that combines the techniques of decision theory and artificial intelligence. Our model uses a modular representation of knowledge that simplifies model building and enables more fully automated decision making. Moreover, the model exploits problem structures to yield better computational efficiency. As an example we apply our techniques to the problem of management of acute deep venous thrombosis.

Investigating the acceptability of a culturally adapted acceptance and commitment therapy group for UK Vietnamese communities: A practice-based feasibility study

Acceptance and Commitment Therapy (ACT) is an empirically supported psychotherapy that offers promise for the mental health of minoritised ethnic populations. Given the diversity of those presenting to inner-city services and barriers to accessing appropriate mental healthcare, we sought to develop a culturally syntonic ACT intervention for UK Vietnamese refugee communities in a practice-based partnership project between a National Health Service and local third-sector service in East London. The aim was to explore the feasibility, acceptability and impact of the adapted intervention to inform culturally inclusive clinical practice and future research. We outline key aspects of Vietnamese belief systems and culture, and consider how these might influence the optimisation of group-based ACT. We then present a mixed-method evaluation of the seven-session adapted ACT group for 11 participants (9 male and 5 female, aged between 44 and 73 years). Individual-level change analyses indicated clinically significant improvements in psychological flexibility for the minority of participants and a mixed pattern for impact on well-being. A thematic analysis and descriptive approach examined acceptability, feasibility and narratives of impact. Participants reported positive feedback on group experience, relevance and usefulness, and emergent themes indicate that the group facilitated key acceptance, commitment and behaviour-change processes, promoted social connections and increased engagement in meaningful life activities in relation to new perspectives and values-based action. Limitations are outlined, but overall, findings suggest preliminary support for the potential beneficial effect of the adapted ACT group as a feasible, culturally acceptable therapeutic approach for UK Vietnamese communities that is worthy of further investigation.

Determining the transmembrane topology of the presenilins

Mutations in two related genes, PS1 (1) and PS2 (2,3) located on chromosomes 14 and 1, respectively, account for the majority of early onset cases of familial Alzheimer's disease (FAD). PS1 and PS2 are predominantly localized in the endoplasmic reticulum and Golgi (4-7). PS1 is a 467 amino acid peptide predicted to contain between seven and nine transmembrane helices based on hydrophobicity profiles (1,8). The protein topology of PS1 and its C. elegans homologues, SEL-12 and HOP-1, have been examined by several investigators (7,9-13). This chapter describes two approaches we utilized to determine the topological orientation of the PS1 N-terminal, and C-terminal domains, and a hydrophilic "loop" region encompassing amino acids 263-407. The first approach is based on the proteolytic sensitivity of amyloid precursor protein (APP) protein chimeras to endoproteolytic cleavage by β-secretase in the lumen of the Golgi. The second approach is based on selective permeabilization of the plasma membrane using a bacterial pore-forming toxin, streptolysin-O (SLO), and subsequent immunocytochemical probing for cytosolic epitopes using specific antibodies. Both of these methods can be easily adapted to determine the topology of other membrane proteins.

DOT1L maintains NK cell phenotype and function for optimal tumor control

Histone methyltransferases (HMTs) are crucial in gene regulation and function, yet their role in natural killer (NK) cell biology within the tumor microenvironment (TME) remains largely unknown. We demonstrate that the HMT DOT1L limits NK cell conversion to CD49a+ CD49b+ intILC1, a subset that can be observed in the TME in response to stimulation with transforming growth factor (TGF)-β and is correlated with impaired tumor control. Deleting Dot1l in NKp46-expressing cells reveals its pivotal role in maintaining NK cell phenotype and function. Loss of DOT1L skews NK cells toward intILC1s even in the absence of TGF-β. Transcriptionally, DOT1L-null NK cells closely resemble intILC1s and ILC1s, correlating with altered NK cell responses and impaired solid tumor control. These findings deepen our understanding of NK cell biology and could inform approaches to prevent NK cell conversion to intILC1s in adoptive NK cell therapies for cancer.

Engaging the private sector as part of HIV pre-exposure prophylaxis service delivery in Vietnam: a comparative analysis of uptake, persistence and HIV seroconversion from 2018 to 2023

Background

In Vietnam, PrEP was introduced in 2017 and scaled up from 2019. Private sector engagement (PSE) in PrEP service delivery was deployed as a strategy from the start to increase PrEP access. We assessed the effectiveness of this approach to inform ongoing efforts to accelerate epidemic control by 2030.

Methods

We implemented a process evaluation with longitudinal design using retrospective programmatic data collected and uploaded onto a secure online system (HMED) from 23 public and 17 private PrEP clinics in Hanoi, Ho Chi Minh City (HCMC), and Dong Nai. We measured the effectiveness of PrEP service delivery by PrEP initiation/reinitiation, uptake, persistence, discontinuation, and HIV seroconversion. We used the Kaplan-Meier time-to-event approach to estimate PrEP persistence and mixed-effects logistic regression analysis to assess factors associated with the PrEP persistence.

Results

From October 2017 to September 2023, 29,944 individuals initiated PrEP, and among these, 79.3% started PrEP at a private sector clinic while 20.7% initiated in a public sector clinic. The median duration of PrEP use persistence at private clinics was significantly longer than that at public clinics (268 days vs. 148 days, respectively). Mixed-effects logistic regression analysis results indicated a significant statistical association between PrEP persistence for at least three months and initiating PrEP at a private clinic [adjusted odds ratio [aOR] = 4.28; 95% confidence interval [CI]: 2.96-6.19], opting for TelePrEP (aOR = 3.42; 95% CI: 2.12-5.53), or being 20 years of age or older (aOR = 1.86; 95% CI: 1.62-2.13). HIV seroconversion was significantly lower among PrEP users at private clinics compared to public clinics (0.03 vs. 0.13 per 100 person-years, respectively; p < 0.01).

Conclusion

Offering choice in PrEP service delivery options is essential to increase access and uptake. Private-sector PrEP providers play a pivotal role in increasing PrEP uptake and coverage in Vietnam, and will be critical to delivery of new long-acting options.