Localization and characterization of the inhibitory Ca2+-binding site of Physarum polycephalum myosin II.

A myosin II is thought to be the driving force of the fast cytoplasmic streaming in the plasmodium of Physarum polycephalum. This regulated myosin, unique among conventional myosins, is inhibited by direct Ca2+ binding. Here we report that Ca2+ binds to the first EF-hand of the essential light chain (ELC) subunit of Physarum myosin. Flow dialysis experiments of wild-type and mutant light chains and the regulatory domain revealed a single binding site that shows moderate specificity for Ca2+. The regulatory light chain, in contrast to regulatory light chains of higher eukaryotes, is unable to bind divalent cations. Although the Ca2+-binding loop of ELC has a canonical sequence, replacement of glutamic acid to alanine in the -z coordinating position only slightly decreased the Ca2+ affinity of the site, suggesting that the Ca2+ coordination is different from classical EF-hands; namely, the specific "closed-to-open" conformational transition does not occur in the ELC in response to Ca2+. Ca2+- and Mg2+-dependent conformational changes in the microenvironment of the binding site were detected by fluorescence experiments. Transient kinetic experiments showed that the displacement of Mg2+ by Ca2+ is faster than the change in direction of cytoplasmic streaming; therefore, we conclude that Ca2+ inhibition could operate in physiological conditions. By comparing the Physarum Ca2+ site with the well studied Ca2+ switch of scallop myosin, we surmise that despite the opposite effect of Ca2+ binding on the motor activity, the two conventional myosins could have a common structural basis for Ca2+ regulation

Prevalence and Concordance of oral and Genital Hpv By Sexual orientation among Us Men

The objective of our study was to describe oral and genital human papillomavirus (HPV) infection prevalence and concordance by sexual orientation among US men using a nationally representative sample. We conducted a retrospective cross-sectional analysis of the 2013-2016 National Health and Nutrition Examination Survey. The survey conducts a physical examination and collects oral rinse and genital swab specimens; demographic and health behaviors are self-reported. We used descriptive statistics and multivariate regression models to estimate HPV infection prevalence and the likelihood of HPV infection, respectively. All analyses were adjusted for National Health and Nutrition Examination Survey design and weights, and statistical significance was tested at a 2-sided P value of less than .05. Men who have sex with men had a statistically significantly higher prevalence of oral HPV (high-risk, 9-valent, 4-valent, and HPV 16 and 18), genital HPV (9-valent, 4-valent, and HPV 16 and 18), and concordant oral and genital HPV (high-risk and 9-valent) infections compared with heterosexual men. Improved HPV prevention among men is needed

The structure of the complex of calmodulin with KAR-2: a novel mode of binding explains the unique pharmacology of the drug

3'-(beta- Chloroethyl)-2',4'-dioxo-3,5'-spiro-oxazolidino-4-deacetoxyvinblastine (KAR-2) is a potent anti-microtubular agent that arrests mitosis in cancer cells without significant toxic side effects. In this study we demonstrate that in addition to targeting microtubules, KAR-2 also binds calmodulin, thereby countering the antagonistic effects of trifluoperazine. To determine the basis of both properties of KAR-2, the three-dimensional structure of its complex with Ca2+-calmodulin has been characterized both in solution using NMR and when crystallized using x-ray diffraction. Heterocorrelation (H-1-N-15 heteronuclear single quantum coherence) spectra of N-15-labeled calmodulin indicate a global conformation change (closure) of the protein upon its binding to KAR-2. The crystal structure at 2.12-Angstrom resolution reveals a more complete picture; KAR-2 binds to a novel structure created by amino acid residues of both the N- and C- terminal domains of calmodulin. Although first detected by x-ray diffraction of the crystallized ternary complex, this conformational change is consistent with its solution structure as characterized by NMR spectroscopy. It is noteworthy that a similar tertiary complex forms when calmodulin binds KAR-2 as when it binds trifluoperazine, even though the two ligands contact (for the most part) different amino acid residues. These observations explain the specificity of KAR-2 as an anti-microtubular agent; the drug interacts with a novel drug binding domain on calmodulin. Consequently, KAR-2 does not prevent calmodulin from binding most of its physiological targets

Social Networks, High-Risk anal Hpv and Coinfection With Hiv in Young Sexual Minority Men

OBJECTIVES: Young sexual minority men (SMM) exhibit a high prevalence and incidence of high-risk genotypes of human papillomavirus (hrHPV) anal infections and a confluence of a high prevalence of HIV and rectal STIs. Social determinants of health (SDOHs) are linked to social network contexts that generate and maintain racial disparities in HIV and STIs. A network perspective was provided to advance our knowledge of drivers of genotype-specific hrHPV infection and coinfection with HIV. The study also examined whether socially connected men are infected with the same high-risk HPV genotypes and, if so, whether this tendency is conditioned on coinfection with HIV. METHODS: Our sample included 136 young SMM of predominantly black race and their network members of other races and ethnicities, aged 18-29 years, who resided in Houston, Texas, USA. These participants were recruited during 2014-2016 at the baseline recruitment period by network-based peer referral, where anal exfoliated cells and named social and sexual partners were collected. Exponential random graph models were estimated to assess similarity in genotype-specific hrHPV anal infection in social connections and coinfection with HIV in consideration of the effects of similarity in sociodemographic, sexual behavioural characteristics, SDOHs and syphilis infection. RESULTS: Pairs of men socially connected to each other tend to be infected with the same hrHPV genotypes of HPV-16, HPV-45 and HPV-51 or HPV-16 and/or HPV-18. The tendency of social connections between pairs of men who were infected with either HPV-16 or HPV-18 were conditioned on HIV infection. CONCLUSIONS: Networked patterns of hrHPV infection could be amenable to network-based HPV prevention interventions that engage young SMM of predominantly racial minority groups who are out of HIV care and vulnerable to high-risk HPV acquisition

The accuracy of anal Self- and Companion Exams among Sexual Minority Men and Transgender Women: a Prospective analysis

BACKGROUND: Squamous cell carcinoma of the anus (SCCA) annual incidence among sexual minority men with and without HIV is 85/100,000 and 19/100,000 persons, respectively, which is significantly higher than the overall incidence (2/100,000). Incidence may also be higher in transgender women. Since SCCA tumours average ≥30 mm at diagnosis, we assessed the accuracy of individuals to self-detect smaller anal abnormalities. METHODS: Using convenience sampling, the study enrolled sexual minority men and transgender women, aged 25-81 years, in Chicago, Illinois and Houston, Texas, USA, during 2020-2022. Individuals were taught the anal self-examination and anal companion examination (ASE/ACE). Then, a clinician performed a digital anal rectal examination (DARE) before participants conducted the ASE or ACE. The sensitivity, specificity and concordance of the ASE/ACE to detect an abnormality were measured along with factors associated with ASE/ACE and DARE concordance. FINDINGS: Among 714 enrolled individuals, the median age was 40 years (interquartile range, 32-54), 36.8% (259/703) were living with HIV, and 47.0% (334/710), 23.4% (166/710), and 23.0% (163/710) were non-Hispanic white, non-Hispanic Black, and Hispanic, respectively. A total of 94.1% (671/713) identified as cisgendered men, and 5.9% (42/713) as gender minorities. A total of 658 participants completed an ASE and 28 couples (56 partners) completed an ACE. Clinicians detected abnormalities in 34.3% (245/714) of individuals. The abnormalities were a median of 3 mm in diameter. Sensitivity and specificity of the ASE/ACE was 59.6% (95% CI 53.5-65.7%) and 80.2% (95% CI 76.6-83.8%), respectively. Overall concordance was 0.73 (95% CI 0.70-0.76) between ASE/ACE and DARE and increased with increasing anal canal lesion size (p = 0.02). Concordance was lower when participants were older and received ASE/ACE training from a lay person rather than a clinician. INTERPRETATION: Sexual minority men/transgender women may self-detect SCCA when malignant lesions are much smaller than the current mean dimension at presentation of ≥30 mm. FUNDING: National Cancer Institute

Factors affecting the prevalence of strongly and weakly carcinogenic and lower-risk human papillomaviruses in anal specimens in a cohort of men who have sex with men (MSM)

Background: MSM are at higher risk for invasive anal cancer. Twelve human papillomaviruses (HPVs) cause cervical cancer in women (Group 1 high-risk HPVs (hrHPVs)) and 13 HPVs are probable/possible causes (Group 2 hrHPVs) of cervical malignancy. HPVs rarely associated with malignancy are classified as lower-risk HPVs (lrHPVs). Materials and Methods: Dacron-swab anal-cytology specimens were collected from and data complete for 97% (1262/1296) of Multicenter AIDS Cohort Study (MACS) men tested for HPVs using the Linear Array assay. Multivariate Poisson regression analyses estimated adjusted prevalence ratios for Group 1/2 hrHPVs and lrHPVs, controlling for the effects of age, race, ethnicity, sexual partnerships, smoking; HIV-infection characteristics, treatment, and immune status among HIV-infected men. Results: HIV-infected men showed 35-90% higher prevalence of Group 1/2 hrHPVs and lrHPVs than HIV-uninfected men, and higher prevalence of multi-Type, and multiple risk-group infections. CD4+ T-cell count was inversely associated with HPV Group 2 prevalence (p<0.0001). The number of receptive anal intercourse (RAI) partners reported in the 24 months preceding HPV testing predicted higher prevalence of Group 1/2 hrHPVs. Men reporting ≥30 lifetime male sex partners before their first MACS visit and men reporting ≥1 RAI partners during the 24 months before HPV testing showed 17-24% and 13-17% higher prevalence of lrHPVs (p-values ≤0.05). Men reporting smoking between MACS visit 1 and 24 months before HPV testing showed 1.2-fold higher prevalence of Group 2 hrHPVs (p = 0.03). Both complete adherence to CART (p = 0.02) and HIV load <50 copies/mL (p = 0.04) were protective for Group 1 hrHPVs among HIV-infected men. Conclusions: HIV-infected men more often show multi-type and multi-group HPV infections HIV-uninfected men. Long-term mutual monogamy and smoking cessation, generally, and CART-adherence that promotes (HIV) viremia control and prevents immunosuppression, specifically among HIV-infected MSM, are important prevention strategies for HPV infections that are relevant to anal cancer. © 2013 Wiley et al