Potential application of immobilized streptokinase extracted from Streptococcus equinus VIT_VB2

Streptokinase purified from Streptococcus equinus VIT_VB2 isolated from bovine milk sample was immobilized in various solid supports namely entrapment in agarose gel, calcium alginate beads and gelatin gel by cross-linking with formaldehyde. Immobilization of streptokinase in calcium alginate beads showed maximum efficiency (81.8?±?1.06%) when compared with entrapment with agarose gel (55.6?±?2.17%) and cross-linked gelatin formaldehyde gel (71.0?±?1.54%). The purified SK activity was expressed maximum in calcium alginate (1%) and gelatin gel (0.25%) with 1292.68?±?1.33 and 1121.9?±?1.2?U?mL^?1, respectively. Similarly, SK entrapped in gelatin gel and calcium alginate showed maximum in vitro blood clot lysis activity with 77.67?±?2.64% and 76.16?±?2.72%, respectively. The immobilized SK in gelatin gel showed complete clot lysis within 15?min; hence, this application of the study could be used in the treatment of superficial thrombophlebitis, phlebitis, and venous thrombosis. These beads were used for three repeated cycles to check the conversion of substrates into their products, and we concluded that SK can be immobilized in the suitable matrices. Therefore, this helps in the drug-delivery strategies in highly efficient way, moreover, economically competent process in the pharmaceutics.     

scalloped functions in a regulatory loop with vestigial and wingless to pattern the Drosophila wing

 The development of the Drosophila wing involves progressive patterning events. In the second larval instar, cells of the wing disc are allotted wing or notum fates by a wingless-mediated process and dorsal or ventral fates by the action of apterous and wingless. Notch-mediated signalling is required for the expression of the genes vestigial and scalloped in the presumptive wing blade. Later, wingless, Notch and cut are involved in cell fate specification along the wing margin. The function of scalloped in this process is not well understood and is the focus of this study. We show that patterning downstream of Notch and wingless pathways is altered in scalloped mutants. Reduction in scalloped expression results in a loss of expression of wing blade- and margin-specific markers. Misexpression of scalloped in the presumptive wing causes misexpression of scalloped, vestigial and wingless reporter genes. However, high levels of scalloped expression have a negative influence on wingless, vestigial and its own expression. Our results demonstrate that scalloped functions in a level-dependent manner in the presumptive wing blade in a loop that involves vestigial and itself. We suggest that wing development requires the regulated expression of scalloped together with vestigial–the ”wing formation” effects of Vestigial in other imaginal discs are probably due to its interaction with the scalloped gene product normally expressed in these discs. Received: 6 May 1998 / Accepted: 22 July 1998     

The story of science: successes,failures, luck,privilege, and bias

I am incredibly honored to receive the 2021 WICB Junior Award for Excellence in Research in WICB’s golden jubilee year. In this essay, I traverse my scientific journey starting with my PhD, highlighting the highs and the lows and how these intersect with luck, privilege, and bias.

V. AnanthanarayananMy pursuit for a PhD started with a hiccup—I had applied to several places in the United States, but barely got any offers due to the economic upheaval that happened that year (2008). I had to forgo any dreams of a PhD in the United States and remained in Bangalore, India to complete a project I had started with William (Bill) Thies at Microsoft Research India on a programming language for expressing biology protocols. Applying to U.S. schools was an expensive task, one which I was unwilling to put my family through again. So, a year later, when I recommenced my search for a PhD position, I set my sights on Europe. I had heard about the PhD program at the Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG ) at Dresden from a friend who had just joined the institute for her PhD. Fortunately, I received an interview call from MPI-CBG. At the end of a crucial interview week at Dresden, I “matched” with Iva Tolic´’s (now Institut Ruđer Boškovic´, Croatia) lab for my PhD. At the start of my PhD, I knew next to nothing about the cytoskeleton, motor proteins, or microscopy, but I found Iva and my lab members to be some of the warmest and most welcoming people. I made friends for life and graduated with a PhD in Biophysics, with a thesis focused on understanding the regulation of the motor protein cytoplasmic dynein. I was lucky to have been able to get a position at MPI-CBG and join Iva’s lab—of the other three places in Europe I had applied to for a PhD, only one other institute invited me for an interview, which also proved to be unsuccessful.On completing my PhD in 2014, I didn’t quite know what I wanted to do. Due to personal reasons, I had to return to India and was open to options in both industry and academia. But with my training in motor protein and cytoskeleton research, I had some ideas for exploring scientific questions related to dynein activation. However, most labs I approached for a postdoctoral position were not open to a project that was outside the realm of their research focus. Nonetheless, Iva, Nenad Pavin (University of Zagreb), and Jonathon (Joe) Howard (Yale University), who were members of my thesis advisory committee, gave me the courage to continue in academia. In my naïveté, I went ahead and applied for the INSPIRE Faculty Fellowship, which is targeted at fresh PhDs and junior postdoctoral fellows to establish their own independent group at an Indian institute. To my surprise, I ended up getting the fellowship. The next issue was finding a host institute that was preferably in Bangalore, where my partner was based. I applied at a few different places, but only after I attended IndiaBioscience’s Young Investigator Meeting in 2014 did I get the chance to meet representatives of potential host institutes, including the Indian Institute of Science (IISc). After a couple of research seminars at IISc, my application was assessed and I was offered the position of INSPIRE Faculty Fellow at the newly formed Centre for BioSystems Science and Engineering, IISc.While I did not have any additional start-up funding, I was given the infrastructure and the independence to pursue my research program. It was slow and frustrating at the start, not unlike most starting labs. I always wondered if it might have been easier if I had had a regular postdoctoral stint. During this time, I also started recognizing how hard it was to be a woman in Indian academia. As a woman principal investigator, one’s authority, expertise, and ability are constantly called into question. Justifying your presence in academia on a daily basis is an exhausting task. I had a great mentor in Sandhya Visweswariah (IISc) who helped me navigate the system. I also had an extremely supportive partner, who kept me going through some of the worst times. Eventually, my lab and I landed on our feet (more about this in “My INSPIRE’d Journey”). Our research has been recognized with grants and awards, but one of the most rewarding parts of the job is seeing other lab members discovering the joy of science (I wrote about my approach to mentorship recently [https://www.nature.com/articles/s41580-020-0256-6]).Three years into the faculty fellowship, I was able to transition to an Assistant Professor position in the same institute. However, this did not change my experience as a young woman in Indian science, and the implicit and explicit biases continued. In 2020, I accepted a fantastic opportunity to further my lab’s science as an EMBL Australia Group Leader at the Single Molecule Science Node at UNSW Sydney and made the move during a pandemic. My lab’s research focus is in understanding how stochastic and rare events pertaining to cytoskeleton and motor proteins give rise to complexity in intracellular organization. With this theme as the essence of our research, we ask specific questions about motor protein regulation to effect differential cellular trafficking, mitochondria-microtubule interactions, and their role in mitochondrial dynamics, and we aim to determine barcodes of global organelle positioning in health and disease.I have the privilege of being able-bodied, born in an upper middle-class family to college-educated parents who were extremely supportive of my choices. I have also inordinately benefitted from the fact that I was born to an Indian ‘upper caste’ family. I therefore had an undue head start in life. These were circumstances beyond my control and yet played a huge role in how my story turned out. I was embarrassingly ignorant of the rampant misogyny in academia until I had to contend with explicit and implicit gender-based biases myself when I started my independent research group in India. Women make up ∼40% of science PhDs awarded in India but represent only ∼13% of Indian academia (biaswatchindia.com), highlighting the stark gender biases at play in creating a leaky pipeline. While I tried my best to voice my discontent and affect changes to create an equitable environment within my department and institute, it was slow work. In 2020, when the pandemic hit and all conferences and meetings went virtual, conference posters advertised on social media made it immediately apparent just how much women were underrepresented in Indian STEM conferences. So, I teamed up with Shruti Muralidhar (now a scientist at Deep Genomics, Canada) to found BiasWatchIndia, an initiative to document women representation and combat gender-biased panels in Indian STEM conferences.BiasWatchIndia has been in existence for a little over a year now—we have achieved several milestones, but there’s still so much to do. “Manels” (conferences that feature only men) are still as rampant as they were when we first started—40% of all Indian STEM conferences are manels. And while we have just about started to tackle the underrepresentation of women in Indian STEM, we are conscious of the intersectionality of bias with gender, caste, ableism, and socioeconomic background and aim to understand how best we can advocate for all minorities.People who are in power in academia and who oppose equity, diversity, and inclusion initiatives and instead preach merit and equality as the gold standard need to introspect, because when options and opportunities are offered without consideration to the millennia of oppression based on gender, race, and background, it is not promoting equality but upholding values that will continue to oppress underrepresented groups. Still, I am optimistic and hope to see real changes that will result in equity in academia in my lifetime.     

Purification of a recombinant histidine-tagged lactate dehydrogenase from the malaria parasite,Plasmodium vivax,and characterization of its properties

Lactate dehydrogenase (LDH) of the malaria parasite, Plasmodium vivax (Pv), serves as a drug target and immunodiagnostic marker. The LDH cDNA generated from total RNA of a clinical isolate of the parasite was cloned into pRSETA plasmid. Recombinant his-tagged PvLDH was over-expressed in E. coli Rosetta2DE3pLysS and purified using Ni²⁺-NTA resin giving a yield of 25–30 mg/litre bacterial culture. The recombinant protein was enzymatically active and its catalytic efficiency for pyruvate was 5.4 × 10⁸ min^?1 M^?1, 14.5 fold higher than a low yield preparation reported earlier to obtain PvLDH crystal structure. The enzyme activity was inhibited by gossypol and sodium oxamate. The recombinant PvLDH was reactive in lateral flow immunochromatographic assays detecting pan- and vivax-specific LDH. The soluble recombinant PvLDH purified using heterologous expression system can facilitate the generation of vivax LDH-specific monoclonals and the screening of chemical compound libraries for PvLDH inhibitors.     

3,4-Methylenedioxy-β-nitrostyrene Inhibits NLRP3 Inflammasome Activation by Blocking Assembly of the Inflammasome

The NLRP3 inflammasome is a critical component of the innate immune system. NLRP3 activation is induced by diverse stimuli associated with bacterial infection or tissue damage, but its inappropriate activation is involved in the pathogenesis of inherited and acquired inflammatory diseases. However, the mechanism by which NLRP3 is activated remains poorly understood. In this study, we explored the role of kinases in NLRP3 inflammasome activation by screening a kinase inhibitor library and identified 3,4-methylenedioxy-β-nitrostyrene (MNS) as an inhibitor for NLRP3 inflammasome activation. Notably, MNS did not affect the activation of the NLRC4 or AIM2 (absent in melanoma 2) inflammasome. Mechanistically, MNS specifically prevented NLRP3-mediated ASC speck formation and oligomerization without blocking potassium efflux induced by NLRP3 agonists. Surprisingly, Syk kinase, the reported target of MNS, did not mediate the inhibitory activity of MNS on NLRP3 inflammasome activation. We also found that the nitrovinyl group of MNS is essential for the inhibitory activity of MNS. Immunoprecipitation, mass spectrometry, and mutation studies suggest that both the nucleotide binding oligomerization domain and the leucine-rich repeat domain of NLRP3 were the intracellular targets of MNS. Administration of MNS also inhibited NLRP3 ATPase activity in vitro, suggesting that MNS blocks the NLRP3 inflammasome by directly targeting NLRP3 or NLRP3-associated complexes. These studies identified a novel chemical probe for studying the molecular mechanism of NLRP3 inflammasome activation which may advance the development of novel strategies to treat diseases associated with abnormal activation of NLRP3 inflammasome.     

A rapid,efficient, and economical inverse polymerase chain reaction-based method for generating a site saturation mutant library

With the development of deep sequencing methodologies, it has become important to construct site saturation mutant (SSM) libraries in which every nucleotide/codon in a gene is individually randomized. We describe methodologies for the rapid, efficient, and economical construction of such libraries using inverse polymerase chain reaction (PCR). We show that if the degenerate codon is in the middle of the mutagenic primer, there is an inherent PCR bias due to the thermodynamic mismatch penalty, which decreases the proportion of unique mutants. Introducing a nucleotide bias in the primer can alleviate the problem. Alternatively, if the degenerate codon is placed at the 5′ end, there is no PCR bias, which results in a higher proportion of unique mutants. This also facilitates detection of deletion mutants resulting from errors during primer synthesis. This method can be used to rapidly generate SSM libraries for any gene or nucleotide sequence, which can subsequently be screened and analyzed by deep sequencing.     

Recombinant extracellular domains of tetraspanin proteins are potent inhibitors of the infection of macrophages by human immunodeficiency virus type 1

Human immunodeficiency virus type 1 (HIV-1) infection of human macrophages can be inhibited by antibodies which bind to the tetraspanin protein CD63, but not by antibodies that bind to other members of the tetraspanin family. This inhibitory response was limited to CCR5 (R5)-tropic virus and was only observed using macrophages, but not T cells. Here, we show that recombinant soluble forms of the large extracellular domain (EC2) of human tetraspanins CD9, CD63, CD81, and CD151 produced as fusion proteins with glutathione S-transferase (GST) can all potently and completely inhibit R5 HIV-1 infection of macrophages with 50% inhibitory concentration values of 0.11 to 1.2 nM. Infection of peripheral blood mononuclear cells could also be partly inhibited, although higher concentrations of EC2 proteins were required. Inhibition was largely coreceptor independent, as macrophage infections by virions pseudotyped with CXCR4 (X4)-tropic HIV-1 or vesicular stomatitis virus (VSV)-G glycoproteins were also inhibited, but was time dependent, since addition prior to or during, but not after, virus inoculation resulted in potent inhibition. Incubation with tetraspanins did not decrease CD4 or HIV-1 coreceptor expression but did block virion uptake. Colocalization of fluorescently labeled tetraspanin EC2 proteins and HIV-1 virions within, and with CD4 and CXCR4 at the cell surfaces of, macrophages could be detected, and internalized tetraspanin EC2 proteins were directed to vesicular compartments that contained internalized dextran and transferrin. Collectively, the data suggest that the mechanism of inhibition of HIV-1 infection by tetraspanins is at the step of virus entry, perhaps via interference with binding and/or the formation of CD4-coreceptor complexes within microdomains that are required for membrane fusion events.     

A novel one-pot 'green' synthesis of stable silver nanoparticles using soluble starch

Stable silver nanoparticles have been synthesized by using soluble starch as both the reducing and stabilizing agents; this reaction was carried out in an autoclave at 15 psi, 121 degrees C for 5 min. Nanoparticles thus prepared are found to be stable in aqueous solution over a period of three months at room temperature (approximately 25 degrees C). The size of these nanoparticles was found to be in the range of 10-34 nm as analyzed using transmission electron micrographs. The X-ray diffraction analysis revealed the face-centred cubic (fcc) geometry of silver nanoparticles. Iodometric titration confirmed the entrapment of silver nanoparticles inside the helical amylose chain. These silver nanoparticles embedded in soluble starch produced a typical emission peak at 553 nm when excited at 380 nm. The use of environmentally benign and renewable materials like soluble starch offers numerous benefits of eco-friendliness and compatibility for pharmaceutical and biomedical applications.     

Critical Role of Endothelial Hydrogen Peroxide in Post-Ischemic Neovascularization

Background

Reactive oxygen species (ROS) play an important role in angiogenesis in endothelial cells (ECs) in vitro and neovascularization in vivo. However, little is known about the role of endogenous vascular hydrogen peroxide (H₂O₂) in postnatal neovascularization.

Methodology/Principal Findings

We used Tie2-driven endothelial specific catalase transgenic mice (Cat-Tg mice) and hindlimb ischemia model to address the role of endogenous H₂O₂ in ECs in post-ischemic neovascularization in vivo. Here we show that Cat-Tg mice exhibit significant reduction in intracellular H₂O₂ in ECs, blood flow recovery, capillary formation, collateral remodeling with larger extent of tissue damage after hindlimb ischemia, as compared to wild-type (WT) littermates. In the early stage of ischemia-induced angiogenesis, Cat-Tg mice show a morphologically disorganized microvasculature. Vascular sprouting and tube elongation are significantly impaired in isolated aorta from Cat-Tg mice. Furthermore, Cat-Tg mice show a decrease in myeloid cell recruitment after hindlimb ischemia. Mechanistically, Cat-Tg mice show significant decrease in eNOS phosphorylation at Ser1177 as well as expression of redox-sensitive vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemotactic protein-1 (MCP-1) in ischemic muscles, which is required for inflammatory cell recruitment to the ischemic tissues. We also observed impaired endothelium-dependent relaxation in resistant vessels from Cat-Tg mice.

Conclusions/Significance

Endogenous ECs-derived H₂O₂ plays a critical role in reparative neovascularization in response to ischemia by upregulating adhesion molecules and activating eNOS in ECs. Redox-regulation in ECs is a potential therapeutic strategy for angiogenesis-dependent cardiovascular diseases.