Biology subjects

Arora, T.

Publications and source records attributed to Arora, T..

3 recordsLinked to original sources

bioRxiv2025

The axonal ER couples translation and secretion machineries for local delivery of axonal transmembrane proteins to promote axonal development

Neuronal development and function rely on the polarized sorting of transmembrane proteins (TMPs). Most TMPs follow a conventional secretory pathway confined to the cell soma, where ER-translated TMPs exit the ER through ERES to reach the Golgi, prior to PM delivery. We recently found that the axonal ER regulates local translation; however, how this is linked to secretion remains unknown. Here, we find that axonally translated TMPs exit the ER and reach the axonal PM via an ERES-dependent/Golgi-independent route. Intriguingly, we uncover a feedback loop linking translation and secretion at axonal ERES. HDLBP-dependent TMP synthesis regulates ERES formation, and axonal ERES in turn modulate TMP translation. Subsequently, the NRZ-SEC22B tethering complex links local TMP ER exit to PM delivery, dependent on ER-PM contacts. Axonal ERES and these associated molecular players support axon growth and bouton assembly. We propose a novel mechanism in which coupling of axonal TMP synthesis and secretion is essential for neuronal development.

cell biology↗

bioRxiv2024

Distinct Motor Map Characteristics for Biceps and Triceps Muscles in Persons with Chronic Tetraplegia: Implications for Arm Function

Following spinal cord injury (SCI), intact neural resources undergo widespread reorganization within the brain. Animal models reveal motor cortical representations devoted to spared muscles above injury expand at the expense of territories occupied by weaker muscles. In this study, we investigated whether motor representations are similarly reorganized between a relatively spared biceps muscle and a weakened triceps muscle in persons with chronic tetraplegia following traumatic cervical SCI in association with upper limb motor function. Twenty-four adults with cervical SCI and 15 able-bodied participants underwent motor mapping using transcranial magnetic stimulation. We determined following map characteristics: area, amplitude (maximal motor evoked potential and volume), and center of gravity. Maximal voluntary contraction (MVC) and motor function (Capabilities of the Upper Extremity Test or CUE-T) were also assessed. Findings reveal that participants with SCI had hyper-excitable biceps maps than triceps, and hyper-excitable biceps maps also compared to biceps maps in able-bodied participants. Higher amplitude of biceps and triceps maps was associated with better motor function (higher CUE-T) and more distal injury (i.e., more spared segments) in persons with SCI. Amplitudes of biceps but not the triceps maps were associated with higher muscle MVCs. In conclusion, over-excitable biceps than triceps map in SCI may represent deafferentation plasticity. For the first time, we demonstrate how map reorganization of spared and weaker muscles in persons with chronic cervical SCI is associated with upper limb motor status. Use-dependent mechanisms may shift neural balance in favor of spared muscles, supporting potential use as response biomarkers in rehabilitation studies. New & NoteworthyOur study reports evidence in humans with cervical SCI that motor representation for the relatively spared muscle becomes hyper-excitable compared to that for the weaker muscle to the extent that hyper-excitability is even higher compared to biceps maps in uninjured individuals. Use-dependent mechanisms likely favor such heightened excitability of spared maps. For the first time, we demonstrate clinical relevance of map excitability in humans with SCI, supporting potential use as a biomarker of recovery.

neuroscience↗

bioRxiv2019

Regulation of Ascorbic acid by gonadotropins in rat Ovary

The dose dependent depletion of ovarian Ascorbic acid (AA) in rat ovaries, has been used as a bioassay for measurement of Luteinizing Hormone (LH). However, the mechanism of action of gonadotropin (LH, FSH) on ascorbic acid depletion is not completely clear in biochemical terms. To elucidate the mechanism, we looked for the pathways; one, where L-Gulonate Dehydrogenase (L-GuDH) catalyzes the conversion of L-Gulonic acid (L-GuA) to L-Xylulose, and, in the second the pathway conversion of L-GuA to AA, in a cats, dogs and Rats. Kinetic analysis of the enzyme L-GuDH in vitro showed the inhibitory effect of AA on L-GuDH. Therefore, we hypothesized that gonadotropins (FSH and LH) may regulate the L-GuDH maintain level of AA in ovary. LH administration to super-ovulated immature female rats caused depletion of ovarian AA but did not result in any change in the specific activity of the ovarian L-GuDH. Further, we administrated a surrogate FSH like hormone (PMSG) to immature female rats which, resulted in increased specific activity of ovarian L-GuDH. However, microarray data on RNA from ovaries exposed to FSH like hormone such as Pregnant Mare serum Gonadotropin (PMSG) did not reveal any increased expression of L-GuDH transcript. It is therefore concluded from the results obtained that; that neither LH, in decreasing the ovarian AA, nor FSH, in increasing the ovarian AA do so by regulating the activity of enzyme L-GuDH at transcriptional level. The results obtained have also been discussed by giving emphasis on the mechanism of ovarian ascorbic acid regulation of LH and FSH.

zoology↗