Emergence of slip-ideal-slip behavior in tip-links serve as force filters of sound in hearing.

Tip-links in the inner ear convey force from sound and trigger mechanotransduction. Here, we present evidence that tip-links (collectively as heterotetrameric complexes of cadherins) function as force filters during mechanotransduction. Our force-clamp experiments reveal that the tip-link complexes show slip-ideal-slip bond dynamics. At low forces, the lifetime of the tip-link complex drops monotonically, indicating slip-bond dynamics. The ideal bond, rare in nature, is seen in an intermediate force regime where the survival of the complex remains constant over a wide range. At large forces, tip-links follow a slip bond and dissociate entirely to cut-off force transmission. In contrast, the individual tip-links (heterodimers) display slip-catch-slip bonds to the applied forces. While with a phenotypic mutant, we showed the importance of the slip-catch-slip bonds in uninterrupted hearing, our coarse-grained Langevin dynamics simulations demonstrated that the slip-ideal-slip bonds emerge as a collective feature from the slip-catch-slip bonds of individual tip-links.

Anisotropy in mechanical unfolding of protein upon partner-assisted pulling and handle-assisted pulling.

Proteins as force-sensors respond to mechanical cues and regulate signaling in physiology. Proteins commonly connect the source and response points of mechanical cues in two conformations, independent proteins in end-to-end geometry and protein complexes in handshake geometry. The force-responsive property of independent proteins in end-to-end geometry is studied extensively using single-molecule force spectroscopy (SMFS). The physiological significance of the complex conformations in force-sensing is often disregarded as mere surge protectors. However, with the potential of force-steering, protein complexes possess a distinct mechano-responsive property over individual force-sensors. To decipher, we choose a force-sensing protein, cadherin-23, from tip-link complex and perform SMFS using end-to-end geometry and handshake complex geometry. We measure higher force-resilience of cadherin-23 with preferential shorter extensions in handshake mode of pulling over the direct mode. The handshake geometry drives the force-response of cadherin-23 through different potential-energy landscapes than direct pulling. Analysis of the dynamic network structure of cadherin-23 under tension indicates narrow force-distributions among residues in cadherin-23 in direct pulling, resulting in low force-dissipation paths and low resilience to force. Overall, the distinct and superior mechanical responses of cadherin-23 in handshake geometry than single protein geometry highlight a probable evolutionary drive of protein-protein complexes as force-conveyors over independent ones.

Broken force dispersal network in tip-links by the mutations at the Ca2+-binding residues induces hearing-loss.

Tip-link as force-sensor in hearing conveys the mechanical force originating from sound to ion-channels while maintaining the integrity of the entire sensory assembly in the inner ear. This delicate balance between structure and function of tip-links is regulated by Ca2+-ions present in endolymph. Mutations at the Ca2+-binding sites of tip-links often lead to congenital deafness, sometimes syndromic defects impairing vision along with hearing. Although such mutations are already identified, it is still not clear how the mutants alter the structure-function properties of the force-sensors associated with diseases. With an aim to decipher the differences in force-conveying properties of the force-sensors in molecular details, we identified the conformational variability of mutant and wild-type tip-links at the single-molecule level using FRET at the endolymphatic Ca2+ concentrations and subsequently measured the force-responsive behavior using single-molecule force spectroscopy with an Atomic Force Microscope (AFM). AFM allowed us to mimic the high and wide range of force ramps (103-106 pN s-1) as experienced in the inner ear. We performed in silico network analysis to learn that alterations in the conformations of the mutants interrupt the natural force-propagation paths through the sensors and make the mutant tip-links vulnerable to input forces from sound stimuli. We also demonstrated that a Ca2+ rich environment can restore the force-response of the mutant tip-links which may eventually facilitate the designing of better therapeutic strategies to the hearing loss.

Force-activated catalytic pathway accelerates bacterial adhesion against flow.

Mechanical cues often influence the factors affecting the transition states of catalytic reactions and alter the activation pathway. However, tracking the real-time dynamics of such activation pathways is limited. Using single-molecule trapping of reaction intermediates, we developed a method that enabled us to perform one reaction at one site and simultaneously study the real-time dynamics of the catalytic pathway. Using this, we showed single-molecule calligraphy at nanometer resolution and deciphered the mechanism of the sortase A enzymatic reaction that, counter-intuitively, accelerates bacterial adhesion under shear tension. Our method captured a force-induced dissociation of the enzyme-substrate bond that accelerates the forward reaction 100×, proposing a new mechano-activated catalytic pathway. In corroboration, our molecular dynamics simulations in the presence of force identified a force-induced conformational switch in the enzyme that accelerates proton transfer between CYS184 (acceptor) and HIS120 (donor) catalytic dyads by reducing the inter-residue distances. Overall, the present study opens up the possibility of studying the influence of factors affecting transition states in real time and paves the way for the rational design of enzymes with enhanced efficiency.

Identification of burden hotspots and risk factors for cholera in India: An observational study.

BACKGROUND: Even though cholera has existed for centuries and many parts of the country have sporadic, endemic and epidemic cholera, it is still an under-recognized health problem in India. A Cholera Expert Group in the country was established to gather evidence and to prepare a road map for control of cholera in India. This paper identifies cholera burden hotspots and factors associated with an increased risk of the disease. METHODOLOGY/PRINCIPLE FINDINGS: We acquired district level data on cholera case reports of 2010-2015 from the Integrated Disease Surveillance Program. Socioeconomic characteristics and coverage of water and sanitation was obtained from the 2011 census. Spatial analysis was performed to identify cholera hotspots, and a zero-inflated Poisson regression was employed to identify the factors associated with cholera and predicted case count in the district. 27,615 cholera cases were reported during the 6-year period. Twenty-four of 36 states of India reported cholera during these years, and 13 states were classified as endemic. Of 641 districts, 78 districts in 15 states were identified as "hotspots" based on the reported cases. On the other hand, 111 districts in nine states were identified as "hotspots" from model-based predicted number of cases. The risk for cholera in a district was negatively associated with the coverage of literate persons, households using treated water source and owning mobile telephone, and positively associated with the coverage of poor sanitation and drainage conditions and urbanization level in the district. CONCLUSIONS/SIGNIFICANCE: The study reaffirms that cholera continues to occur throughout a large part of India and identifies the burden hotspots and risk factors. Policymakers may use the findings of the article to develop a roadmap for prevention and control of cholera in India.

Effect of complete decongestive therapy and home program on health- related quality of life in post mastectomy lymphedema patients.

BACKGROUND: Secondary lymphedema is common in women treated for breast cancer. It may be a result of surgery or radiotherapy. Edema commonly affects the arm, leading to discomfort, reduced arm movements, pain and diminished quality of life. Therefore, the relationship between post mastectomy lymphedema and quality of life has evolved as an important criteria in treatment of breast cancer survivors. METHODS: Sixty breast cancer survivors who developed post mastectomy lymphedema were recruited. Patients were divided into 2 groups (n = 30) according to the treatment they received; Conventional therapy (CT) and Complete Decongestive Therapy (CDT) groups. Measurements were taken at baseline, 4 and 6 weeks. Health related Quality of Life was evaluated with the EORTC QLQ C30 and EORTC QLQ-BR23 questionnaires. Pain was measured using the Visual Analogue Scale. Descriptive statistics were used to analyze participant demographics and repeated measures of ANOVA was used for within and between group comparisons. RESULTS: Both groups showed improved quality of life and diminished pain after 6 weeks of treatment. However, greater improvement was observed in CDT group compared to the CT group. CONCLUSION: In this study, remedial exercises and home program in addition to manual lymphatic drainage and compression bandaging resulted in improved quality of life. Early identification of lymphedema and incorporation of remedial exercises and a home program improve the quality of life for breast cancer survivors. TRIAL REGISTRATION: Trial registry ID: ISRCTN13242080 , Date of registration: 7 April 2016.

Effect of complete decongestive therapy and a home program for patients with post mastectomy lymphedema.

[Purpose] Post mastectomy lymphedema is common among breast cancer survivors. It leads to physical discomfort and functional impairment. Rehabilitation forms the mainstay of treatment and is multidisciplinary. [Subjects and Methods] Sixty post mastectomy patients were allocated randomly and assigned to either a conventional treatment group (n=30) or a complete decongestive therapy (CDT) group (n=30). The conventional treatment group received manual lymphatic drainage, wore a low elastic compression garment, received glenohumeral mobilization, and performed deep breathing exercises, and the complete decongestive therapy group received CDT from a trained physiotherapist and a daily home program along with the conventional treatment, 5 days a week for 6 weeks. [Results] Arm circumference measurements were taken at five levels: the wrist, mid forearm, elbow, mid-upper arm, and axilla. The upper extremity function was evaluated using the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, and pain was assessed using the visual analogue scale. Measurements were taken at baseline, and at 4th and 6th weeks after the start of intervention. Within and between group comparisons showed significant improvements in the CDT group. [Conclusion] Complete decongestive therapy and a home program assists breast cancer related lymphedema survivors in regaining their lost functions. It also helps to improve their independence in daily activities, reduce their need for caregivers, and thereby improving their quality of life. Therefore, the results of this study showed that the CDT with a home program is an effective treatment for reducing post mastectomy lymphedema.