Biology subjects

Chhatre, A.

Publications and source records attributed to Chhatre, A..

4 recordsLinked to original sources

bioRxiv2024

Tubulin tyrosination/detyrosination governs the spatial segregation of intraflagellar transport trains on axonemal microtubule doublets

Assembly and function of cilia rely on the continuous transport of ciliary components between the cell body and the ciliary tip. This is performed by specialized molecular machines, known as Intraflagellar Transport (IFT) trains. Anterograde IFT trains are powered by kinesin-2 motors and move along the B-tubules (enriched in detyrosinated tubulin) of the ciliary microtubule doublets. Conversely, retrograde IFT trains are moved by dynein-1b motors along the A-tubules (enriched in tyrosinated tubulin) back to the cell body. The segregation of oppositely directed trains on A-tubules or B-tubules is thought to prevent traffic jams in the cilium, but the mechanism by which opposite polarity trains are sorted onto either tubule, and whether tubulin tyrosination/detyrosination plays a role in that process, is unknown. Here, we show that CRISPR-mediated knock-out of VashL, the enzyme that detyrosinates microtubules, causes recurrent stoppages of IFT trains and reduces the rate of ciliary growth in Chlamydomonas reinhardtii. To test whether the observed stoppages, potentially caused by collisions between oppositely directed IFT trains, are ascribable to direct interactions between IFT trains and tubulin tyrosination/detyrosination, we developed methods to reconstitute the motility of native IFT trains from cilia on de-membranated axonemes and ex vivo on synthetically polymerized microtubules. We show that anterograde trains have higher affinity for detyrosinated microtubules (analogous to B-tubules), while retrograde trains for tyrosinated microtubules (analogous to A-tubules). We conclude that tubulin tyrosination/detyrosination is required for the spatial segregation of oppositely directed trains and for their smooth uninterrupted motion. Our results provide a model for how the tubulin code governs molecular transport in cilia.

cell biology↗

bioRxiv2023

Niche homeostasis in multi-lineage stem cell populations is maintained through intercellular redox gradients

Reactive oxygen species (ROS), predominantly derived from mitochondrial respiratory complexes, have emerged as key molecules influencing cell fate decisions like maintenance and differentiation. These redox-dependent events are mainly considered to be cell intrinsic in nature, on the contrary our observations indicate involvement of these oxygen-derived entities as intercellular communicating agents. In Drosophila male germline, Germline Stem Cells (GSCs) and neighbouring Cyst Stem Cells (CySCs) maintain differential redox thresholds where CySC have higher redox-state compared to the adjacent GSCs. Disruption of the redox equilibrium between the two adjoining stem cell populations by depleting Superoxide Dismutases (SODs) especially Sod1 results in deregulated niche architecture and loss of GSCs, which was mainly attributed to loss of contact-based receptions and uncontrolled CySC proliferation due to ROS-mediated activation of self-renewing signals. Our observations hint towards the crucial role of differential redox states where CySCs containing higher ROS function not only as a source of their own maintenance cues but also serve as non-autonomous redox moderators of GSCs. Our findings underscore the complexity of niche homeostasis and predicate the importance of intercellular redox communication in understanding stem cell microenvironments.

developmental biology↗

bioRxiv2021

Surface expressed Plasmodium circumsporozoite protein (CSP) modulates cellular flexibility and motility

Plasmodium falciparum circumsporozoite protein (CSP) is a critically required abundant surface protein of sporozoites and a major vaccine candidate. However, neither the structure nor the role of CSP in sporozoite motility is well understood. Our recent in vitro data, from single-molecule pulling experiments suggested a mechanically pliable structure for P. falciparum CSP. By engineering vegetative cells of the cellular slime-mold Dictyostelium discoideum with regulatable CSP surface expression, we report evidence for direct involvement of CSP towards conferring elastic properties and motility of the cells. With an increase in the surface-CSP levels by 5-8-fold, the Youngs moduli of the cells, observed through atomic force microscopy, decreased around 2-fold, with a concomitant increase in motility by about 2-fold. Interestingly, only full length CSP expression conferred maximal flexibility and motility, as opposed to repeat region alone or the flanking domains of CSP. The enhanced motility of the CSP-expressing cells was abrogated with anti-CSP antibodies as well as phospholipase cleavage of CSP, indicating specific contribution of CSP towards motility. Measurements of the Youngs moduli of Plasmodium berghei midgut (MG) and salivary gland (SG) sporozoites revealed an inverse correlation with CSP levels with a decrease from 1.1 kPa to 0.3 kPa as the CSP concentration doubled from MG to SG sporozoites. We hypothesize that high CSP level lowers the stiffness of sporozoites possibly through its pliable surface-coat, leading to cellular flexibility. These findings may explain a sporozoites developmental ability to enhance its CSP levels during transition from midgut to salivary glands to suit a migratory mode in the host, needed for successful hepatocyte invasion.

cell biology↗

bioRxiv2019

Lis1 regulates Phagocytosis by co-localising with actin in the Phagocytic cup

Phagocytosis, the ingestion of solid particles by cells, is essential for nutrient uptake, innate immune response, antigen presentation and organelle homeostasis. Here we show that Lissencephaly-1 (Lis1), a well-known regulator of the microtubule motor Dynein, also co-localises with actin at the phagocytic cup in the early stages of phagocytosis. Both knockdown and overexpression of Lis1 perturbs phagocytosis, suggesting that an optimum level of Lis1 is required to regulate actin dynamics within the phagocytic cup during particle engulfment. This requirement of Lis1 is replicated in mouse macrophage cells as well as in the amoeba Dictyostelium, indicating an evolutionarily conserved role for Lis1 in phagocytosis. In support of these findings, a general role for Lis1 in regulating actin dynamics is suggested by observing defective migration of cells overexpressing Lis1. Taken together, Lis1 localises to the phagocytic cup and influences actin dynamics in a manner that is important for the uptake of solid particles in cells.

cell biology↗