Biology subjects

Prakriya, M.

Publications and source records attributed to Prakriya, M..

3 recordsLinked to original sources

bioRxiv2022

Octopamine metabolically reprograms astrocytes to confer neuroprotection against α-synuclein

Octopamine is a well-established invertebrate neurotransmitter involved in fight-or-flight responses. In mammals, its function was replaced by norepinephrine. Nevertheless, it is present at trace amounts and can modulate the release of monoamine neurotransmitters by a yet unidentified mechanism. Here, through a multidisciplinary approach utilizing in vitro and in vivo models of -synucleinopathy, we uncovered an unprecedented role for octopamine in driving the conversion from toxic to neuroprotective astrocytes in the cerebral cortex by fostering aerobic glycolysis. Physiological levels of neuron-derived octopamine act on astrocytes via a TAAR1-Orai1-Ca2+-calcineurin-mediated signaling pathway to stimulate lactate secretion. Lactate uptake in neurons via the MCT2-calcineurin-dependent pathway increases ATP and prevents neurodegeneration. Pathological increases of octopamine caused by -synuclein halts lactate production in astrocytes and short-circuits the metabolic communication to neurons. Our work provides a novel function of octopamine as a modulator of astrocyte metabolism and subsequent neuroprotection with implications to -synucleinopathies.

neuroscience↗

bioRxiv2022

Regulation of neuropathic pain by microglial Orai1 channels

Microglia are important mediators of neuroinflammation that underlies neuropathic pain. However, the molecular checkpoints controlling microglial reactivity are not well-understood. We investigated the role of Orai1 channels for microglia-mediated neuroinflammation following nerve injury and find that deletion of Orai1 in microglia attenuates Ca2+ signaling and the production of inflammatory cytokines by proalgesic agonists. Conditional deletion of Orai1 attenuated microglia proliferation in the dorsal horn, spinal cytokines levels, and potentiation of excitatory neurotransmission following peripheral nerve injury. These cellular effects were accompanied by mitigation of pain hyperalgesia in Orai1 knockout mice. A small-molecule Orai1 inhibitor, CM4620, similarly mitigated allodynia in male mice. Surprisingly, these protective effects were not seen in female mice, revealing striking sexual dimorphism in Orai1 regulation of microglial reactivity and hyperalgesia. These findings indicate that Orai1 channels are key regulators of the sexually dimorphic role of microglia for the neuroinflammation that underlies neuropathic pain.

neuroscience↗

bioRxiv2022

A human tubular aggregate myopathy mutation unmasks STIM1-independent rapid inactivation of Orai1 channels

Ca2+ release-activated Ca2+ (CRAC) channels are activated by direct physical interactions between Orai1, the channel protein, and STIM1, the endoplasmic reticulum Ca2+ sensor. A hallmark of CRAC channels is fast Ca2+-dependent inactivation (CDI) which provides negative feedback to limit Ca2+ entry through CRAC channels. Although STIM1 is thought to be essential for mediating CDI, the molecular mechanism of CDI remains largely unknown. Here, we examined a gain-of-function (GOF) human Orai1 disease mutation, L138F, that causes tubular aggregate myopathy (TAM). Through pairwise mutational analysis, we determine that large amino acid substitutions at either L138 or the neighboring T92 locus evoke highly Ca2+-selective currents in the absence of STIM1. We find that the GOF phenotype arises due to steric clash between L138 on TM2 and T92 located on the pore helix. Surprisingly, strongly activating L138 and T92 mutations also show CDI in the absence of STIM1, contradicting prevailing views that STIM1 is required for inactivation. CDI of constitutively open T92W and L138F mutants occurred with similar kinetics as WT Orai1 but showed enhanced intracellular Ca2+ sensitivity, which could be normalized by the addition of STIM1. Truncation of the Orai1 C-terminus reduced T92W CDI consistent with a key role for the Orai1 C-terminus for CDI. Overall, these results elucidate the molecular basis of the human TAM-linked mutation and indicate that CDI of CRAC channels is mediated by an Orai1-intrinsic mechanism with STIM1 tuning the calcium sensitivity of CDI.

physiology↗