Biology subjects

Basak, B.

Publications and source records attributed to Basak, B..

3 recordsLinked to original sources

bioRxiv2020

A genome engineering resource to uncover principles of cellular organization and tissue architecture by lipid signalling

Phosphoinositides (PI) are key regulators of cellular organization in eukaryotes and genes that tune PI signalling are implicated in human disease mechanisms. Biochemical analyses and studies in cultured cells have identified a large number of proteins that can mediate PI signalling. However, the role of such proteins in regulating cellular processes in vivo and development in metazoans remains to be understood. Here we describe a set of CRISPR based genome engineering tools that allow the manipulation of each of these proteins with spatial and temporal control during metazoan development. We demonstrate the use of these reagents to deplete a set of 103 proteins individually in the Drosophila eye and identify several new molecules that control eye development. Our work demonstrates the power of this resource in uncovering the molecular basis of tissue homeostasis during normal development and in human disease biology.

genetics↗

bioRxiv2019

Extended synaptotagmin regulates plasma membrane-endoplasmic reticulum contact site structure and lipid transfer function in vivo

Inter-organelle communication between closely apposed membranes is proposed at Membrane Contact Sites (MCS). However the regulation of MCS structure and their functional relevance in vivo remain debated. The extended synaptotagmins (Esyt) are evolutionarily conserved proteins proposed to function at MCS. However, loss of all three Esyts in yeast or mammals shows minimal phenotypes questioning the functional importance of Esyt. We report that in Drosophila photoreceptors, MCS number is regulated by PLC{beta} activity. Photoreceptors of a null allele of Drosophila extended synaptotagmin (dEsyt) show loss of ER-PM MCS. Loss of dEsyt results in mislocalization of RDGB, an MCS localized lipid transfer protein, required for photoreceptor structure and function, ultimately leading to retinal degeneration. dEsyt depletion enhanced the retinal degeneration, reduced light responses and slower rates of plasma membrane PIP2 resynthesis seen in rdgB mutants. Thus, dEsyt function and PLC{beta} signaling regulate ER-PM MCS structure and lipid transfer in Drosophila photoreceptors.

cell biology↗

bioRxiv2019

The lipid transfer function of RDGB at ER-PM contact sites is regulated by multiple interdomain interactions.

In Drosophila photoreceptors, following Phospholipase C-{beta} activation, the phosphatidylinositol transfer protein (PITP) RDGB, is required to maintain lipid homeostasis at endoplasmic reticulum (ER) plasma membrane (PM) membrane contact sites (MCS). Depletion or mis-localization of RDGB results in multiple defects in photoreceptors. Previously, interaction between the FFAT motif of RDGB with the integral ER protein dVAP-A was shown to be important for its localization at ER-PM MCS. Here, we report that in addition to FFAT motif, a large unstructured region (USR1) of RDGB is required to support the RDGB/dVAP-A interaction. However, interaction with dVAP-A alone is insufficient for accurate localization of RDGB: this also requires association of RDGB with apical PM, through its C-terminal LNS2 domain. Deletion of LNS2 domain results in complete mis-localisation of RDGB and also induces large mis-regulated interdomain movements abrogating RDGB function. Thus, multiple independent interactions between individual domains of RDGB supports its function at ER-PM MCS.

cell biology↗