Reconstitution of the phosphodiesterase 6 maturation process important for photoreceptor cell function.

The sixth family phosphodiesterases (PDE6) are principal effector enzymes of the phototransduction cascade in rods and cones. Maturation of nascent PDE6 protein into a functional enzyme relies on a coordinated action of ubiquitous chaperone HSP90, its specialized cochaperone aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1), and the regulatory Pγ-subunit of PDE6. Deficits in PDE6 maturation and function underlie severe visual disorders and blindness. Here, to elucidate the roles of HSP90, AIPL1, and Pγ in the maturation process, we developed the heterologous expression system of human cone PDE6C in insect cells allowing characterization of the purified enzyme. We demonstrate that in the absence of Pγ, HSP90, and AIPL1 convert the inactive and aggregating PDE6C species into dimeric PDE6C that is predominantly misassembled. Nonetheless, a small fraction of PDE6C is properly assembled and fully functional. From the analysis of mutant mice that lack both rod Pγ and PDE6C, we conclude that, in contrast to the cone enzyme, no maturation of rod PDE6AB occurs in the absence of Pγ. Co-expression of PDE6C with AIPL1 and Pγ in insect cells leads to a fully mature enzyme that is equivalent to retinal PDE6. Lastly, using immature PDE6C and purified chaperone components, we reconstituted the process of the client maturation in vitro. Based on this analysis we propose a scheme for the PDE6 maturation process.

Estimation of Access to Safe Drinking Water to Households in Etawah District: A Cross-Sectional Study.

CONTEXT: Unsafe drinking water causes diarrheal disease and environmental enteropathy. The quality of water is determined by its physical, chemical, and biological characteristics. Water sources have a significant impact on household members' health, particularly children. To combat this, India is committed to providing household tap connections to ensure the delivery of safe drinking water with the "Jal Jeevan Mission." AIMS: This study aims to estimate the access to safe drinking water and the physical and chemical qualities of water (qualitatively) in the urban and rural areas of Etawah district, India. SETTINGS AND DESIGN: A cross-sectional study was conducted in Etawah district from January 2020 to December 2021. The study subjects were the eldest female of the family. A total of 312 females were included. The data collected were analyzed using IBM SPSS Statistics for Windows, version 25 (released 2017; IBM Corp., Armonk, New York, United States) for descriptive analysis. RESULTS: In the present study, 76.3% (238/312) of households in the urban and rural areas had access to safe drinking water (here, the meaning of the word "safe" is based on its operational definition). A total of 130 (83.3%) households in rural areas and only 21 (13.5%) in urban areas had private supply as the primary water source. The physical and chemical qualities of water were within the requirement (acceptable limit) and permissible limit in all the study areas, so the water is considered safe for drinking. CONCLUSIONS: This study reported that 76.3% (238) households had access to safe drinking water according to the operational definition. The major public source of drinking water was public-supplied tap water, and in private sources, submersible or boreholes were the most common.

Barriers of household toilet utilization among toilet owners in a rural area of Northern India: An analytical cross-sectional study.

Background: Open defecation continues to prevail among toilet owners despite effective implementation of the Swachh Bharat Mission (Gramin). We conducted this study to determine toilet utilization rates and learn about the barriers to toilet use in the rural areas. By understanding the barriers, physicians can provide targeted education and become better equipped to manage their patients' conditions and advocate for their demands. Materials and Methods: We conducted a cross-sectional study on the households of the rural field practice areas of the department in central Uttar Pradesh by the census method. House listing was procured from the departmental records. The questionnaire was directed at both the household level and individual level. Results: The proportion of households with access to a toilet was found to be 91.1% of which 504 households were included in the study. Among the toilet owners, 115 (22.8%) households were not using toilets exclusively by all the members. At the individual level, age groups (of 20-59 years, and ≥60 years) and female gender were found to be significantly associated with open defecation. At the household level, government assistance for toilet construction and livestock keeping was found to be associated with open defecation. Major barriers to toilet use were childhood habits, dearth of toilets in the farming grounds/workplace, women during menstruation and having a non-functional toilet. Conclusion: This study indicates that merely installing a household toilet does not ensure exclusive utilization of toilet and the practice of open defecation might continue to be prevalent if corrective measures are not undertaken.

Insulin sensitization by small molecules enhancing GLUT4 translocation.

Insulin resistance (IR) is the root cause of type II diabetes, yet no safe treatment is available to address it. Using a high throughput compatible assay that measures real-time translocation of the glucose transporter glucose transporter 4 (GLUT4), we identified small molecules that potentiate insulin action. In vivo, these insulin sensitizers improve insulin-stimulated GLUT4 translocation, glucose tolerance, and glucose uptake in a model of IR. Using proteomic and CRISPR-based approaches, we identified the targets of those compounds as Unc119 proteins and solved the structure of Unc119 bound to the insulin sensitizer. This study identifies compounds that have the potential to be developed into diabetes treatment and establishes Unc119 proteins as targets for improving insulin sensitivity.

Unique interface and dynamics of the complex of HSP90 with a specialized cochaperone AIPL1.

Photoreceptor phosphodiesterase PDE6 is central for visual signal transduction. Maturation of PDE6 depends on a specialized chaperone complex of HSP90 with aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1). Disruption of PDE6 maturation underlies a severe form of retina degeneration. Here, we report a 3.9 Å cryoelectron microscopy (cryo-EM) structure of the complex of HSP90 with AIPL1. This structure reveals a unique interaction of the FK506-binding protein (FKBP)-like domain of AIPL1 with HSP90 at its dimer interface. Unusually, the N terminus AIPL1 inserts into the HSP90 lumen in a manner that was observed previously for HSP90 clients. Deletion of the 7 N-terminal residues of AIPL1 decreased its ability to cochaperone PDE6. Multi-body refinement of the cryo-EM data indicated large swing-like movements of AIPL1-FKBP. Modeling the complex of HSP90 with AIPL1 using crosslinking constraints indicated proximity of the mobile tetratricopeptide repeat (TPR) domain with the C-terminal domain of HSP90. Our study establishes a framework for future structural studies of PDE6 maturation.

Frmpd1 Facilitates Trafficking of G-Protein Transducin and Modulates Synaptic Function in Rod Photoreceptors of Mammalian Retina.

Trafficking of transducin (Gαt) in rod photoreceptors is critical for adaptive and modulatory responses of the retina to varying light intensities. In addition to fine-tuning phototransduction gain in rod outer segments (OSs), light-induced translocation of Gαt to the rod synapse enhances rod to rod bipolar synaptic transmission. Here, we show that the rod-specific loss of Frmpd1 (FERM and PDZ domain containing 1), in the retina of both female and male mice, results in delayed return of Gαt from the synapse back to outer segments in the dark, compromising the capacity of rods to recover from light adaptation. Frmpd1 directly interacts with Gpsm2 (G-protein signaling modulator 2), and the two proteins are required for appropriate sensitization of rod-rod bipolar signaling under saturating light conditions. These studies provide insight into how the trafficking and function of Gαt is modulated to optimize the photoresponse and synaptic transmission of rod photoreceptors in a light-dependent manner.

Modified Bain's Circuit as an Alternate to Non-invasive Ventilation in COVID 19.

Introduction COVID-19 is a pandemic that severely affects the lungs. Symptomatically affected individuals often become severely hypoxic, requiring non-invasive ventilation. The scarcity of resources in resource-compromised countries like India led to the adoption of novel strategies like using Bain's circuit for assisting spontaneous ventilation. This study compares the outcome when a standard circuit is replaced with a shortened Bain's circuit. Aims and objectives To compare shortened Bain's circuit and bilevel positive airway pressure (BiPAP) in spontaneously ventilated COVID 19 patients with regards to effects on hemodynamic stability and efficacy of ventilation using blood gas analysis. Methodology Twenty-four COVID patients aged between 35-70 years, requiring non-invasive ventilation but not tolerating BiPAP or not improving on BiPAP were enrolled in the study. Baseline heart rate and arterial blood gases (ABG) were recorded. Patients were then ventilated using shortened Bain's circuit. Heart rate and ABG were then recorded two hours after ventilation. Results Hemodynamic and blood gas parameters were comparable between the two groups at baseline and on BiPAP. Group A showed better hemodynamic and blood gas profiles compared to group B, but the difference was not statistically significant because of small sample size. Conclusion Shortened Bain's circuit may be a viable alternative to non-invasive ventilation in spontaneously breathing hypoxic patients with efficacy comparable to a standard Bain's circuit and reduced chances of carbon dioxide retention. Studies with a larger sample size are needed to further validate the conclusion.

Assessment of knowledge and their practices regarding malaria among members of Village Health Sanitation Committee in rural Uttar Pradesh: A cross-sectional study.

Background: In 2019, the global number of malaria cases was estimated at 229 million. An estimated 409,000 deaths were attributed to malaria in 2019. Under-five children are the most susceptible to malaria, accounting for 67% (274,000) of all malaria deaths worldwide in 2019. This study aimed to assess knowledge and practices regarding malaria among Village Health Sanitation Committee (VHSC) members in rural Uttar Pradesh. Methodology: This cross-sectional study was conducted in the villages of four districts of Uttar Pradesh with high malaria burden. In the present study, 484 participants were interviewed from four districts of Uttar Pradesh. Results: Nearly all the participants (97.1%) have heard about malaria. Majority of the participants (97.1) were aware that mosquito bites spread malaria. However, many participants were also having a false awareness that malaria is spread by other modes like drinking contaminated water, touching each other, eating contaminated food, and so on. More than half of the participants told that mosquitoes are responsible for malaria breeds in stagnant clean water (25.6%) and stagnant dirty water (28.5%). Nearly half of them were aware that mosquitoes' biting time was sunset (42.1%) and sunrise (7.8%). Conclusion: In the present study, many participants were having a false awareness that malaria is spread by other modes like drinking contaminated water, touching each other, eating contaminated food, and so on. Even the knowledge regarding any government program for the prevention and control of malaria of the mosquitoes was very weak. There is an urgent requirement of increasing knowledge among the VHSC members to reduce the malaria burden in the country.

Are the labour rooms of primary healthcare facilities capable of providing basic delivery and newborn services? A cross-sectional study.

OBJECTIVES: The study aimed to assess the functionality of labour rooms by evaluating the labour room infrastructure with reference to the standard guidelines, the status of the availability of human resources, the availability of essential equipment and consumables in the labour room and by documenting the knowledge of the healthcare provider in terms of labour room practices. The study also explored the facility parameters associated with its delivery load taking the facility as a unit of analysis. DESIGN: A cross-sectional analytical study. SETTING: India has realised the importance of improving the quality of care in public health facilities, and steps are being taken to make healthcare more responsive to women's needs. With an increase in the proportion of institutional deliveries in India, the outcome of the delivery process can be improved by optimising the health facility components. PARTICIPANTS: The study was conducted in 52 health facilities and healthcare providers involved in the delivery process in the selected facilities. RESULTS: The infrastructure of the facilities was found to be the best for medical college followed by district hospitals, Community Health Centres (CHCs), Primary Health Centres (PHCs) and subcentres. Similar findings were observed in terms of the availability of equipment and consumables. Lack of healthcare providers was observed as only 20% of the posts for health personnel were fulfilled in CHCs followed by PHCs, subcentres and district hospitals where 43, 50 and 79% of the available vacancies were fulfilled. The level of knowledge of healthcare providers in terms of partograph, active management of the third stage of labour and post-partum haemorrhage ranged as per their designation. The specialists were the most knowledgeable while the Auxiliary Nurse Midwife (AMNs) were the least. All the components of structural capacity, i.e. infrastructure (r 2 = 0.377, P value < 0.001), equipment and consumable (r 2 = 0.606, P value < 0.001) and knowledge of healthcare providers (r 2 = 0.456, P value < 0.001) along with the overall facility score were positively correlated with the average delivery load of the health facility. The results from multivariate linear regression depict significant relation between the delivery load and availability of equipment and consumables (t = 4.015, P < 0.01) and with the knowledge of healthcare providers (t = 2.129, P = 0.039). CONCLUSIONS: The higher facilities were better equipped to provide delivery and newborn care. A higher delivery load was found at high-level facilities which can be attributed to better infrastructure, adequate supply of equipment and consumables and availability of trained human resources.

Pregnancy outcomes and vertical transmission capability of SARS-CoV-2 infection among asymptomatic females: A cross-sectional study in a tertiary care rural hospital.

BACKGROUND: The COVID-19 pandemic is still spreading throughout the world along with its strange and frightening mutations, and the World Health Organization (WHO) has declared it as a global pandemic. OBJECTIVE: The present investigation aims to evaluate the effect of SARS-CoV-2 infection on mother and newborn outcomes and the vertical transmission potential of this virus. STUDY DESIGN: This was a cross-sectional study conducted at a tertiary care dedicated COVID-19 hospital. A total of 40 pregnant females (RT-PCR positive for SARS-CoV-2) and their 41 neonates (including stillbirths and a twin delivery) were included in the present study. RESULTS: All the mothers in the study were SARS-CoV-2 positive on the RT-PCR test, but none had any COVID-19 symptoms (pneumonia-like fever, cough, fatigue, sore throat, shortness of breath, and diarrhea). Out of 41 newborns, 38 (92.7%) were healthy, one (2.4%) was a stillbirth, and two newborns (4.9%) could not be revived. All the 41 (100.0%) neonates, including stillborn and preterm were negative for the SARS-CoV-2 RT-PCR test. Twenty-Six neonates (63.4%) were delivered by caesarean section, whereas 15 cases (36.6%) had a normal vaginal delivery. CONCLUSION: The present study showed no suggestion of vertical transmission of SARS-CoV-2 in pregnant females. Therefore, the placenta might function as a barrier to the SARS-CoV-2 virus. Also, there were no complications come upon during the delivery of any neonate in the present study.

Morbidity Patterns among Menopausal Women in Rural Uttar Pradesh, India: A Cross-Sectional Study.

OBJECTIVES: The quality of life declines gradually as women enter menopause, owing to the various problems associated with estrogen deficiency and aging, which adds to their morbidities. This study aimed to investigate the patterns of morbidity among rural menopausal women and compare the morbidity patterns among menopausal transition group and post-menopausal women. METHODS: This community-based cross-sectional study included menopausal women aged 45-55 years from rural areas of the Etawah district, Uttar Pradesh, India. To select blocks and villages of the district, multistage random sampling was performed. According to a pretested, semistructured schedule, data were collected through interviews. RESULTS: A total of 315 women participated in the study. The most frequent complaints among the participants were of feeling tired and worn out (85.1%) and of muscle and joint pains (67.6%). Poor memory (P = 0.046) and diabetes (P = 0.024) were more common in women who were in the menopause transition phase than in those who were in the postmenopausal phase. CONCLUSIONS: This study showed that majority of the menopausal women suffered from physical problems. Lifestyle modification and awareness programs will be beneficial among women in menopausal transition, to reduce the morbidity later in post-menopausal stage. Behaviour change communication, family and community support are essential in post-menopausal women, to help them cope with various morbid conditions.

Epidemiological characteristics, reinfection possibilities and vaccine development of SARS CoV2: A global review.

According to the World Health Organization (WHO), there are 37,704,153 cases and 10,79,029 deaths due to COVID-19 till the 13th October 2020 in the world. Day by day, rise in the number of COVID-19 deaths has created great pressure on health facilities, governmental bodies, and health workers. There is a need for knowledge regarding lifecycle, transmission, and different strains of SARSCoV2, so that countries can stop the disease as early as possible. The present study was conducted to review various epidemiological aspects along with measures used in the containment and prevention of this new pandemic. The scientific literature database was searched using the terms: coronavirus, 2019-nCoV, SARSCoV2, and COVID-19. Articles with appropriate topics fulfilling the objective of the present work were included. The epidemiological characteristics regarding life-cycle, intermediate hosts, viability on various surfaces, strains, case fatality rate, and their implication to reduce the transmission of SARSCoV2 have been identified. According to Centers for Disease Control and Prevention, Atlanta (updated till October 05, 2020) people with recurrent or persistent positive COVID-19 tests in South Korea and USA did not show to have live virus in their bodies. As per WHO web-page information till 15 October 2020, there were 42 candidate vaccines in clinical evaluation and 156 vaccines are in preclinical evaluation phase. As the virus can easily be transmitted to the people either via droplets, fomites, and may be via the fecal-oral route, knowledge regarding the above-mentioned areas is needed for time to be prepared for the next waves of the COVID-19 pandemic.

Retrospective sequential trend analysis of neoplasms reported in a tertiary care hospital of district Etawah, Uttar Pradesh.

INTRODUCTION: An estimated 2.25 million new cancer cases with 7 lakh cancer deaths were reported, according to GLOBOCAN 2018 in India. There is a steady rise in cancer cases, but trends and patterns vary within the state depending on the geographic region. OBJECTIVES: To study the proportion and site-wise distribution of neoplasm reported at a tertiary care hospital in district Etawah, Uttar Pradesh, India. MATERIAL AND METHODS: A record based retrospective study was conducted at a tertiary care hospital in district Etawah, Uttar Pradesh. Total four years (from 2015 to 2018) hospital-based retrospective data were collected from the Medical Record Department. Identification and distribution of malignant neoplasm were done according to the WHO ICD-10 classification. RESULTS: Total cases diagnosed with malignancy from January 2015 to December 2018 were 3614. Cancer cases reported over the years was 932 (25.8%) in 2015, 1031 (28.5%) cases in 2016, 897 (24.8%) in 2017 and 754 (20.9%) in 2018. It was found that breast carcinoma (24.0%) accounted for the maximum number of cases diagnosed, followed by lung carcinoma (10.9%), cervical cancer (8.7%), gall bladder carcinoma (8%), and oral cavity cancer (7.9%). CONCLUSION: The present study reveals that the malignancy of the breast is most common, followed by malignancies of lung, cervix, and gall bladder among the patients who were seeking care in a tertiary care hospital of the district Etawah Uttar Pradesh, India.

Systemic review of CNS involvement and its manifestations in SARS-CoV2 positive patients.

Coronavirus is known to cause various systemic infections both in human and animal which are mostly mild in nature. However, recent years have seen major pandemics caused by coronavirus which are very invasive and virulent in nature. The recent SARS-CoV2 is a new addition to this list of coronavirus pandemics. So the present study was done to systematically review the CNS involvement and its manifestations in SARS-CoV2 positive patients. Systemic review of article published between 1st Dec 2019 to 31st July 2020 searched through web-based database of MEDLINE (Pubmed) and Google scholar using following keywords "COVID -19" OR "CORONAVIRUS" OR "SARS-CoV2" AND "NEUROLOGICAL" OR "CNS" OR "BRAIN". Using the steps of systemic review eight article were selected for qualitative analysis. Majority of these article were reporting neurological symptoms among patients admitted in different wards along with others general symptoms. None of the study was specifically devoted to study the neurological manifestations and complications in SARS-CoV2 positive patients. The present study concludes that there is a scarcity of good quality research which attempts to establish the role of SARS-CoV2 infection in CNS and its manifestations. However, there are evidences that CNS involvement is present in majority of the patients. Proper documentation of theses involvement and indentification of these into mild, moderate and severe infection will help in early identification and treatment of these patients.

Transducin Partners Outside the Phototransduction Pathway.

Transducin mediates signal transduction in a classical G protein-coupled receptor (GPCR) phototransduction cascade. Interactions of transducin with the receptor and the effector molecules had been extensively investigated and are currently defined at the atomic level. However, partners and functions of rod transducin α (Gαt 1) and ßγ (Gß1γ1) outside the visual pathway are not well-understood. In particular, light-induced redistribution of rod transducin from the outer segment to the inner segment and synaptic terminal (IS/ST) allows Gαt1 and/or Gß1γ1 to modulate synaptic transmission from rods to rod bipolar cells (RBCs). Protein-protein interactions underlying this modulation are largely unknown. We discuss known interactors of transducin in the rod IS/ST compartment and potential pathways leading to the synaptic effects of light-dispersed Gαt1 and Gß1γ1. Furthermore, we show that a prominent non-GPCR guanine nucleotide exchange factor (GEF) and a chaperone of Gα subunits, resistance to inhibitors of cholinesterase 8A (Ric-8A) protein, is expressed throughout the retina including photoreceptor cells. Recent structures of Ric-8A alone and in complexes with Gα subunits have illuminated the structural underpinnings of the Ric-8A activities. We generated a mouse model with conditional knockout of Ric-8A in rods in order to begin defining the functional roles of the protein in rod photoreceptors and the retina. Our analysis suggests that Ric-8A is not an obligate chaperone of Gαt1. Further research is needed to investigate probable roles of Ric-8A as a GEF, trafficking chaperone, or a mediator of the synaptic effects of Gαt1.

Neurological Involvement in COVID-19 Patients: A Narrative Review.

Background Coronavirus disease 2019 (COVID-19) is a viral disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) belonging to the coronavirus family. The primary target of SARS-CoV-2 is peripheral mucosal cells of respiratory tract. Recent days have seen few cases where virus has affected extrapulmonary organ such as nervous system. Materials and Methods The present study was a narrative review done using techniques of systemic review, that is, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic databases such as PubMed (Medline) and Google Scholar were searched systematically for published article from December 1, 2019 to June 5, 2020. A total of 189 articles were initially selected by the authors. A final list of 17 articles was prepared and following information were extracted from selected studies: study design, main result, and limitations of the study. Results Majority of these article were descriptive studies describing spectrum of signs and symptoms among admitted patients. In majority of these studies, patients have developed symptoms suggestive of neurological involvement. Most common central nervous system symptoms reported were headache, followed by dizziness and confusion. Similarly, the most common peripheral nervous system involvement was loss of taste and smell. Conclusion The present study concludes that there are enough evidences to prove that SARS-CoV-2 infection affects both central and peripheral nervous system. Various mechanisms are proposed to explain the pathophysiology of neurological manifestations in COVID-19-positive patients that needs to be established and verified.

Hyperbaric oxygen therapy as an adjuvant to standard therapy in the treatment of diabetic foot ulcers.

BACKGROUND AND AIMS: Chronic diabetic foot ulcers pose a major problem because of associated limb threatening complications. The aim of the present study was to evaluate the efficacy of hyperbaric oxygen therapy (HBOT) as an adjuvant to standard therapy for treatment of diabetic foot ulcers. MATERIAL AND METHODS: A total of 54 patients with diabetic foot ulcer of Wagner grade II-IV were recruited in this prospective, randomized, double blind study. Patients were randomized to receive HBOT along with standard therapy (group H; n = 28) or standard therapy alone (group S; n = 26). Patients were given 6 sessions per week for 6 weeks and followed up for 1 year. Outcomes were measured in terms of healing, and need for amputation, grafting or debridement. Parametric continuous variables were analyzed using Student unpaired t-test and categorical variables were analyzed using Chi square test. RESULTS: The diabetic ulcers in 78% patients in Group H completely healed without any surgical intervention while no patient in group S healed without surgical intervention (P = 0.001). 2 patients in group H required distal amputation while in Group S, three patients underwent proximal amputation. CONCLUSION: The present study shows that hyperbaric oxygen therapy is a useful adjuvant to standard therapy and is a better treatment modality if combined with standard treatment rather than standard treatment alone for management of diabetic foot ulcers.

Analysis of risk factors contributing to road traffic accidents in a tertiary care hospital. A hospital based cross-sectional study.

PURPOSE: Road traffic accidents (RTAs) are a public health issue and cost a lot to individuals, families, communities and nations. Trauma care systems in India are at a nascent stage of development. There is gross disparity between trauma services available in various parts of the country. Rural area in India has inefficient services for trauma care, due to the varied topography, financial constraints, and lack of appropriate health infrastructure. The present study is to study the trends of occurrence of RTA cases by month, week and time of accident occurrence as well as to research the types of vehicle involved in accidents and other various risk factors related to them. METHODS: During 1st January 2017 to 31st December 2017, a hospital-based and cross-sectional study of RTA victims was conducted. The patients were admitted in emergency department of Uttar Pradesh University of Medical Sciences, Saifai, Etawah, when stabilized, they were shifted to the orthopaedics and surgery ward. RESULTS: In the study, 654 road accident victims were included, of which the majority were males (77.5%) and the most of them belonged to rural (67%). RTA victims according to the month of occurrence majority were found in January (12.5%) and evening was time of a day with maximum accidents (32.1%). Mortality cases of RTA victims based on type of road user and it shows decreasing trend of mortality of motorcyclists (54.2%) followed by pedestrian (25.1%). CONCLUSION: There should be control over people driving vehicles under the influence of alcohol and drivers over-speeding and rash driving on urban roads as well as rural village roads.

Ric-8A, a GEF, and a Chaperone for G Protein α-Subunits: Evidence for the Two-Faced Interface.

Resistance to inhibitors of cholinesterase 8A (Ric-8A) is a prominent non-receptor GEF and a chaperone of G protein α-subunits (Gα). Recent studies shed light on the structure of Ric-8A, providing insights into the mechanisms underlying its interaction with Gα. Ric-8A is composed of a core armadillo-like domain and a flexible C-terminal tail. Interaction of a conserved concave surface of its core domain with the Gα C-terminus appears to mediate formation of the initial Ric-8A/GαGDP intermediate, followed by the formation of a stable nucleotide-free complex. The latter event involves a large-scale dislocation of the Gα α5-helix that produces an extensive primary interface and disrupts the nucleotide-binding site of Gα. The distal portion of the C-terminal tail of Ric-8A forms a smaller secondary interface, which ostensibly binds the switch II region of Gα, facilitating binding of GTP. The two-site Gα interface of Ric-8A is distinct from that of GPCRs, and might have evolved to support the chaperone function of Ric-8A.