Structural changes of tumor necrosis factor alpha associated with membrane insertion and channel formation.

Low pH enhances tumor necrosis factor alpha (TNF)-induced cytolysis of cancer cells and TNF-membrane interactions that include binding, insertion, and ion-channel formation. We have also found that TNF increases Na+ influx in cells. Here, we examined the structural features of the TNF-membrane interaction pathway that lead to channel formation. Fluorometric studies link TNF's acid-enhanced membrane interactions to rapid but reversible acquisition of hydrophobic surface properties. Intramembranous photolabeling shows that (i) protonation of TNF promotes membrane insertion, (ii) the physical state of the target bilayer affects the kinetics and efficiency of TNF insertion, and (iii) binding and insertion of TNF are two distinct events. Acidification relaxes the trimeric structure of soluble TNF so that the cryptic carboxyl termini, centrally located at the base of the trimer cone, become susceptible to carboxypeptidase Y. After membrane insertion, TNF exhibits a trimeric configuration in which the carboxyl termini are no longer exposed; however, the proximal salt-bridged Lys-11 residues as well as regional surface amino acids (Glu-23, Arg-32, and Arg-44) are notably more accessible to proteases. The sequenced cleavage products bear the membrane-restricted photoreactive probe, proof that surface-cleaved TNF has an intramembranous disposition. In summary, the trimer's structural plasticity is a major determinant of its channel-forming ability. Channel formation occurs when cracked or partially splayed trimers bind and penetrate the bilayer. Reannealing leads to a slightly relaxed trimeric structure. The directionality of bilayer penetration conforms with x-ray data showing that receptor binding to the monomer interfaces of TNF poises the tip of the trimeric cone directly above the target cell membrane.     

Using Natural Language Processing on Electronic Health Records to Enhance Detection and Prediction of Psychosis Risk

BackgroundUsing novel data mining methods such as natural language processing (NLP) on electronic health records (EHRs) for screening and detecting individuals at risk for psychosis. MethodThe study included all patients receiving a first index diagnosis of nonorganic and nonpsychotic mental disorder within the South London and Maudsley (SLaM) NHS Foundation Trust between January 1, 2008, and July 28, 2018. Least Absolute Shrinkage and Selection Operator (LASSO)-regularized Cox regression was used to refine and externally validate a refined version of a five-item individualized, transdiagnostic, clinically based risk calculator previously developed (Harrell’s C = 0.79) and piloted for implementation. The refined version included 14 additional NLP-predictors: tearfulness, poor appetite, weight loss, insomnia, cannabis, cocaine, guilt, irritability, delusions, hopelessness, disturbed sleep, poor insight, agitation, and paranoia. ResultsA total of 92 151 patients with a first index diagnosis of nonorganic and nonpsychotic mental disorder within the SLaM Trust were included in the derivation (n = 28 297) or external validation (n = 63 854) data sets. Mean age was 33.6 years, 50.7% were women, and 67.0% were of white race/ethnicity. Mean follow-up was 1590 days. The overall 6-year risk of psychosis in secondary mental health care was 3.4 (95% CI, 3.3–3.6). External validation indicated strong performance on unseen data (Harrell’s C 0.85, 95% CI 0.84–0.86), an increase of 0.06 from the original model. ConclusionsUsing NLP on EHRs can considerably enhance the prognostic accuracy of psychosis risk calculators. This can help identify patients at risk of psychosis who require assessment and specialized care, facilitating earlier detection and potentially improving patient outcomes.     

An evaluation of factors associated with sexual risk taking among Black men who have sex with men: a comparison of younger and older populations

In the United States, rates of human immunodeficiency virus (HIV) infection are highest among Black men who have sex with men (BMSM). Prior research indicates that younger BMSM in particular (i.e., BMSM 29 years of age and younger) are most at risk for HIV infection, and that HIV incidence in this subpopulation has risen in recent years. It remains unclear, however, why younger BMSM, relative to BMSM 30 years of age and older, are at increased risk for HIV infection. For the current study, we surveyed 450 BMSM located in the Atlanta, GA metropolitan and surrounding areas. We assessed BMSM’s depressive symptoms, substance use during sex, psycho-social risk factors (i.e., HIV risk perceptions, condom use self-efficacy, internalized homophobia, and perceived HIV stigmatization), and sexual risk taking (i.e., condomless anal intercourse [CAI]). We found that younger BMSM (YBMSM) and older BMSM (OBMSM) differed with respect to factors associated with CAI. In multivariable models, alcohol use before or during sex, lower educational attainment, and sexual orientation (i.e., bisexual sexual orientation) were significantly associated with increased CAI for YBMSM, while HIV risk perceptions and internalized homophobia were significantly, negatively associated with CAI among OBMSM. Rates of engaging in CAI were similar across the two age cohorts; however, factors related to CAI varied by these two groups. Findings emphasize the need to consider targeted interventions for different generational cohorts of BMSM.