Biology subjects

Maneesha S Inamdar

Publications and source records attributed to Maneesha S Inamdar.

3 recordsLinked to original sources

bioRxiv2016

Networks that link cytoskeletal regulators and diaphragm proteins underpin filtration function in Drosophila nephrocytes.

Insect nephrocytes provide a valuable model for kidney disease, as they are structurally and functionally homologous to mammalian kidney podocytes. They possess an exceptional macromolecular assembly, the nephrocyte diaphragm (ND), which serves as a filtration barrier and helps maintain tissue homeostasis by filtering out wastes and toxic products. However, the nephrocyte architecture and elements that maintain the ND are not understood. We show that Drosophila nephrocytes have a unique cytoplasmic cluster of F-actin, which is maintained by the microtubule cytoskeleton and Rho-GTPases. A balance of Racl and Cdc42 activity as well as proper microtubule organization is required for positioning the actin cluster. Further, ND proteins Sns and Duf also localize to this cluster and regulate organization of the actin and microtubule cytoskeleton. Perturbation of any of these inter-dependent components impairs nephrocyte ultrafiltration. Thus cytoskeletal components, Rho-GTPases and ND proteins work in concert to maintain the specialized nephrocyte architecture and function.

Cell Biology↗

bioRxiv2016

Differential modulation of the cellular and humoral immune responses in Drosophila is mediated by the endosomal ARF1-Asrij axis

How multicellular organisms maintain immune homeostasis across various organs and cell types is an outstanding question in immune biology and cell signaling. In Drosophila, blood cells (hemocytes) respond to local and systemic cues to mount an immune response. While endosomal regulation of Drosophila hematopoiesis is reported, the role of endosomal proteins in cellular and humoral immunity is not well-studied. Here we demonstrate a functional role for endosomal proteins in immune homeostasis. We show that the ubiquitous trafficking protein ADP Ribosylation Factor 1 (ARF1) and the hemocyte-specific endosomal regulator Asrij differentially regulate humoral immunity. ARF1 and Asrij mutants show reduced survival and lifespan upon infection, indicating perturbed immune homeostasis. The ARF1-Asrij axis suppresses the Toll pathway anti-microbial peptides (AMPs) by regulating ubiquitination of the inhibitor Cactus. The Imd pathway is inversely regulated-while ARF1 suppresses AMPs, Asrij is essential for AMP production. Several immune mutants have reduced Asrij expression, suggesting that Asrij co-ordinates with these pathways to regulate the immune response. Our study highlights the role of endosomal proteins in modulating the immune response by maintaining the balance of AMP production. Similar mechanisms can now be tested in mammalian hematopoiesis and immunity.

Immunology↗

bioRxiv2016

A Key Cytoskeletal Regulator of Ubiquitination Amplifies TGFβ Signaling during Mouse Developmental Vascular Patterning

Vascular development involves de novo formation of a capillary plexus, which is then pruned and remodeled by angiogenic events. Cytoskeletal remodeling and directional endothelial migration are essential for developmental and pathological angiogenesis. Smad-dependent TGF{beta} signaling controls vascular patterning and is negatively regulated by microtubules. Here we show that a positive regulator of TGF{beta} signaling is essential for developmental vascular patterning and microtubule stability. Rudhira/BCAS3 is known to bind microtubules and to play a nodal role in cytoskeletal remodeling and directional endothelial cell (EC) migration in vitro. We demonstrate that the molecular and cellular function of Rudhira is deployed at critical steps in vascular patterning. We generated the first floxed mice for rudhira and find that global or endothelial knockout of rudhira results in mid-gestation lethality due to aberrant embryonic and extra-embryonic vessel patterning and defective cardiac morphogenesis. Rudhira null yolk sac ECs show random and retarded migration. Yolk sac transcriptome analysis revealed key mediators of angiogenic processes and TGF{beta} receptor signaling were perturbed in rudhira null mutants. Molecular and biochemical analyses showed that rudhira depletion reduced microtubule stability but increased expression of pathway inhibitors leading to high levels of SMAD2/3 ubiquitination and reduced activation. These effects were not rescued by exogenous TGF{beta}. However, TGF{beta} treatment of wild type ECs increased Rudhira expression. Further, exogenous Rudhira, which promotes directional cell migration, caused increased SMAD2/3 nuclear translocation and reduced inhibitor levels. Therefore, we propose that Rudhira and TGF{beta} signaling are mutually dependent. Rudhira has a dual function in promoting TGF{beta} signaling, possibly by sequestering microtubules and simultaneously preventing SMAD2/3 ubiquitination to permit EC migration and vascular patterning. TGF{beta} signaling and aberrant human Rudhira (Breast Cancer Amplified Sequence 3, BCAS3) expression are both associated with tumour metastasis. Our study identifies a cytoskeletal, cell type-specific modulator of TGF{beta} signaling important in development and cancer.

Developmental Biology↗