Biology subjects

Ghosh, D. K.

Publications and source records attributed to Ghosh, D. K..

3 recordsLinked to original sources

bioRxiv2026

A Functional Placenta-On-Chip Model For Maternal-Fetal Transport

The human placenta functions as a highly specialised barrier that integrates trophoblast differentiation, endocrine activity, and regulated transport of molecules to sustain fetal development. Experimental interrogation of placental barrier function remains challenging due to limited access to human placental tissue and the complexity of existing in vitro models. Here, we report a static, two-chamber placenta-on-chip platform designed to recapitulate key structural and functional attributes of the human placental barrier within an experimentally accessible format. The device design prioritises open maternal compartmentalisation and diffusion-dominated transport, reflecting the haemochorial nature of human placentation. It also remains compatible with standard multi-well plate formats for parallel experimentation. In this two-chambered device, separated by an extracellular matrix-loaded/coated microporous membrane, the trophoblast supports trophoblast syncytialisation, sustained {beta}-human chorionic gonadotropin secretion, and selective barrier function. The engineered barrier restricts macromolecular transport while permitting controlled diffusion of small solutes. Glucose transport across the device is strongly dependent on cellular configuration, with inclusion of the endothelial layer significantly modulating nutrient flux and yielding fetal-to-maternal glucose ratios comparable to those reported in vivo. The platform further supports directional transfer of urea from the fetal to the maternal compartment, demonstrating bidirectional metabolite exchange relevant to placental waste clearance. Under hyperglycemic conditions, glucose transport across the barrier increases without evidence of barrier breakdown, indicating sensitivity to metabolic perturbation. This scalable design of a placenta-on-chip platform provides a robust framework for studying placental transport, metabolic regulation, and barrier integrity. It offers broad application in placental biology, pregnancy-associated pathologies, and screening for pregnancy-safe drugs.

bioengineering↗

bioRxiv2019

HYPK scaffolds the Nedd8 and LC3 proteins to initiate the formation of autophagosome around the poly-neddylated huntingtin exon1 aggregates

Selective degradation of protein aggregates by autophagy is an essential homeostatic process of safeguarding cells from the effects of proteotoxicity. Among the ubiquitin-like modifier proteins, Nedd8 conjugation to misfolded proteins is prominent in stress-induced protein aggregates, albeit the function of neddylation in autophagy is unclear. Here, we report that polyneddylation functions as a post-translational modification for autophagic degradation of proteotoxic-stress induced protein aggregates. We also show that HYPK functions as an autophagy receptor in the polyneddylation-dependent aggrephagy. The scaffolding function of HYPK is facilitated by its C-terminal ubiquitin-associated domain and N-terminal tyrosine-type LC3 interacting region which bind to Nedd8 and LC3 respectively. Both Nedd8 and HYPK are positive modulators of basal and induced-autophagy, leading to desensitizing cells from protein aggregates, such as aggregates of mutant huntingtin-exon1. Thus, we propose an additive role of neddylation and HYPK in clearance of protein aggregates by autophagy, resulting in cytoprotective effect during proteotoxic stress.

cell biology↗

bioRxiv2018

Control of eNOS and nNOS through regulation of obligatory conformational changes in the reductase catalytic cycle

Endothelial and neuronal nitric oxide synthases (eNOS, nNOS) are important signal generators in a number of processes including angiogenesis and neurotransmission. The homologous inducible isoform (iNOS) occupies a multitude of conformational states in a catalytic cycle, including subnanosecond input and output states and a distribution of open conformations with average lifetimes of ~4.3 ns. In this study, fluorescence lifetime spectroscopy was used to probe conformational states of purified eNOS and nNOS in the presence of chaotropes, calmodulin, NADP+ and NADPH. Two-domain FMN/oxygenase constructs of nNOS were also examined with respect to calmodulin effects. Optical biosensing was used to analyze calmodulin binding in the presence of NADP+ and NADPH. Calmodulin binding induced a shift of the population away from the input and to the open and output states of NOS. NADP+ shifted the population towards the input state. The oxygenase domain, lacking the input state, provided a measure of calmodulin-induced open-output transitions. A mechanism for regulation by calmodulin and an elucidation of the catalytic mechanism are suggested by a conformational lockdown model. Calmodulin speeds transitions between input and open and between open and output states, effectively reducing the conformational manifold, speeding catalysis. Conformational control of catalysis involves reorientation of the FMN binding domain, of which fluorescence lifetime is an indicator. The approach described herein is a new tool for biophysical and structural analysis of NOS enzymes, regulatory events and other homologous reductase-containing enzymes.\n\nA note to the readerThis manuscript has over the past several years been submitted to and rejected by several journals, usually on the basis of reviewer opinion that it was not an important enough result to merit inclusion in the journal. Owing to the passing of the first author and the loss of his expertise in fluorescence lifetime spectroscopy, it has become too onerous a task to continually revise the manuscript to suit the whims of reviewers who nevertheless still reject the work. We are thus simply releasing the final form of the manuscript to BioRxiv in the hopes that it finds a readership who will find, as we do, that the results are of value to the field.

biochemistry↗