Biology subjects

Malla, A. P.

Publications and source records attributed to Malla, A. P..

4 recordsLinked to original sources

bioRxiv2021

D-cysteine is an endogenous regulator of neural progenitor cell dynamics in the mammalian brain

D-amino acids are increasingly recognized as important signaling molecules in the mammalian central nervous system. However, the D-stereoisomer of the amino acid with the fastest in vitro spontaneous racemization rate, cysteine, has not been examined in mammals. Using chiral high-performance liquid chromatography and an stereospecific luciferase assay, we identify endogenous D-cysteine in the mammalian brain. We identify serine racemase (SR), which generates the NMDA glutamate receptor co-agonist D-serine, as a candidate biosynthetic enzyme for D-cysteine. Levels of D-cysteine are enriched over twentyfold in the embryonic mouse brain compared to the adult. D-cysteine reduces the proliferation of cultured mouse embryonic neural progenitor cells (NPCs) by approximately 50%, effects not shared with D-serine or L-cysteine. The antiproliferative effect of D-cysteine is mediated by the transcription factors FoxO1 and FoxO3a. The selective influence of D-cysteine on NPC proliferation is reflected in overgrowth and aberrant lamination of the cerebral cortex in neonatal SR knockout mice. Finally, we perform an unbiased screen for D-cysteine-binding proteins in NPCs by immunoprecipitation with a D-cysteine-specific antibody followed by mass spectrometry. This approach identifies myristoylated alanine-rich C-kinase substrate (MARCKS) as a putative D-cysteine-binding protein. Together, these results establish endogenous mammalian D-cysteine and implicate it as a physiologic regulator of NPC homeostasis in the developing brain.

neuroscience↗

bioRxiv2020

Cocaine receptor identified as BASP1

Cocaine is a behavioral stimulant with substantial abuse potential related to its positively rewarding actions 1,2. Cocaine inhibits the reuptake inactivation of neurotransmitters such as dopamine, serotonin, and norepinephrine at high nanomolar to low micromolar concentrations 2. There is evidence for substantially more potent influences of cocaine. For instance, Calligaro and Eldefrawi reported binding of [3H]cocaine to brain membranes with a dissociation constant of about 16 nM 3. At 10 nM concentration, cocaine elicits environmental place conditioning in planarians 4. Furthermore, 1nM cocaine enhances dopamine D2 receptor agonist-mediated signaling 5. Inhibition of amine reuptake by cocaine is substantially less potent than some of these high affinity actions. Thus, evidence for a specific, high affinity receptor for cocaine that mediates its behavioral actions has been lacking. We now report high affinity binding of cocaine to the membrane-associated brain acid soluble protein-1 (BASP1) with a Kd of 7 nM. Knocking down BASP1 in the striatum inhibits [3H]cocaine binding to striatal synaptosomes. Depletion of BASP1 in the nucleus accumbens diminishes locomotor stimulation, acquisition, and expression of locomotor sensitization to cocaine. Our findings indicate that BASP1 is a pharmacologically relevant receptor for cocaine and a putative therapeutic target for psychostimulant addiction.

pharmacology and toxicology↗

bioRxiv2019

Functional intra-operative guidance of the cavernous nerve network using near-infrared cyanine voltage-sensitive dye imaging: relevance for nerve-sparing radical prostatectomy

Despite current progress achieved in the surgical technique of radical prostatectomy, post-operative complications such as erectile dysfunction and urinary incontinence persist at high incidence rates. In this paper, we present a methodology for functional intra-operative localization of the cavernous nerve (CN) network for nerve-sparing radical prostatectomy using near-infrared cyanine voltage-sensitive dye (VSD) imaging, which visualizes membrane potential variations in the CN and its branches (CNB) in real time. As a proof-of-concept experiment, we demonstrate a functioning complex nerve network in response to electrical stimulation of the CN, which was clearly differentiated from surrounding tissues in an in vivo rat prostate model. Stimulation of an erection was confirmed by correlative intracavernosal pressure (ICP) monitoring. Within 10 minutes, we performed trans-fascial staining of the CN by direct VSD administration. Our findings suggest the applicability of VSD imaging for real-time, functional imaging guidance during nerve-sparing radical prostatectomy.

biophysics↗

bioRxiv2018

Transcranial photoacoustic imaging of NMDA-evoked focal circuit dynamics in rat forebrain

Transcranial functional photoacoustic (fPA) voltage-sensitive dye (VSD) imaging promises to overcome current temporal and spatial limitations of current neuroimaging modalities. The technique previously distinguished global seizure activity from control neural activity in groups of rats. To validate the focal specificity of transcranial fPA neuroimaging in vivo, we now present proofs-of-concept that the results differentiate between low- and high-dose N-methyl-D-aspartate (NMDA) evoked neural activity in rat hippocampus. Concurrent quantitative EEG (qEEG) and microdialysis recorded real-time circuit dynamics and glutamate concentration change, respectively. We hypothesized that location-specific fPA VSD contrast would identify the neural dynamics in hippocampus with the correlation to NMDA evoked focal glutamate release and time-specific EEG signals. To test the hypothesis, we infused 0.3 to 3.0 mM NMDA at 2 l/min over 60 min via an implanted microdialysis probe. The dialysate samples collected every 20 min during the infusion were analyzed for focal changes in extracellular glutamate release. Transcranial fPA VSD imaging provided NMDA-evoked VSD responses with positive correlation to extracellular glutamate concentration change at the contralateral side of the microdialysis probe. The graded response represents the all-or-none gating system of the dentate gyrus (DG) in hippocampus. Quantitative EEG (qEEG) successfully confirmed induction of focal seizure activity during NMDA infusion. We conclude that transcranial fPA VSD imaging distinguished graded DG gatekeeping functions, based on the VSD redistribution mechanism sensitive to electrophysiologic membrane potential. The results suggest the potential future use of this emerging technology in clinics and science as an innovative and significant functional neuroimaging modality.

neuroscience↗