Biology subjects

Ronnekleiv, O. K.

Publications and source records attributed to Ronnekleiv, O. K..

6 recordsLinked to original sources

bioRxiv2026

Identifying Novel Estrogenic Mitochondrial Targets in Hypothalamic Proopiomelanocortin Neurons by Chemoproteomics

Loss of estrogens at menopause is linked to impaired brain metabolism and increased risk of Alzheimers disease (AD). However, estrogen replacement therapies are limited due to the deleterious effects of estrogen on peripheral organs and increased risk of vascular dementia. We have developed a non-steroidal estrogenic compound, STX, which does not bind to the classical estrogen receptors and {beta}, but mimics estrogenic signaling in the central nervous system (CNS) without the peripheral reproductive actions. STX is protective against neurodegeneration in stroke and AD models, but its molecular targets are unknown. Here, we identified and validated STX neural targets using chemoproteomic, molecular biological, electrophysiological and metabolic assays of hypothalamic proopiomelanocortin (POMC) neurons. Chemoproteomic profiling identified voltage dependent anion channels (VDAC1-3) as major intracellular binding partners in mHypo43 (POMC) cells. Based on quantitative single-cell PCR, Vdac2 was identified as the dominant isoform in female hypothalamic POMC neurons. Seahorse metabolic flux analyses showed that STX potently increased glycolysis, oxidative respiration and mitochondrial ATP production in mHypo43 cells. Nanomolar concentrations of STX enhanced VDAC2 voltage-dependent gating in reconstituted lipid membranes and shifted the low-conductance states toward anion selectivity, consistent with increased ATP flux. Together, these findings reveal a mechanism for the neuroprotective effects of STX through enhancing mitochondrial bioenergetics and modulating VDAC channel properties, potentially increasing cellular energy stores. Therefore, this work identifies previously unrecognized estrogenic mitochondrial targets and provides a mechanistic basis for the neuroprotective actions of STX relevant to menopause-associated brain vulnerability.

neuroscience↗

bioRxiv2025

Melanocortin-responsive Kiss1 neurons of the arcuate nucleus drive energy expenditure through glutamatergic signaling to the dorsomedial hypothalamus.

Energy expenditure (EE) is essential for metabolic homeostasis, yet its central regulation remains poorly understood. Here, we identify arcuate Kiss1 neurons as key regulators of EE in male mice. Ablation of these neurons induced obesity, while their chemogenetic activation increased brown adipose tissue (BAT) thermogenesis without affecting food intake. This action is mediated by glutamatergic projections from Kiss1ARC neurons to CART/Lepr-expressing neurons in the dorsomedial hypothalamus, which activate the raphe pallidus-BAT pathway. CRISPR-mediated deletion of the vesicular glutamate transporter 2 (Vglut2) from Kiss1ARC neurons replicated the obesogenic effect. Furthermore, deletion of the melanocortin 4 receptor (MC4R) from Kiss1 neurons resulted in obesity, reduced energy expenditure and impaired thermogenesis. Optogenetic stimulation of pro-opiomelanocortin (POMC) fibers evoked inward currents in Kiss1 neurons, that were attenuated by MC4R antagonism. Our findings reveal a previously unrecognized neural circuit that mediates melanocortin action on energy expenditure, offering new insights into central mechanisms of metabolic control.

neuroscience↗

bioRxiv2024

Estradiol elicits distinct firing patterns in arcuate nucleus kisspeptin neurons of females through altering ion channel conductances

Hypothalamic kisspeptin (Kiss1) neurons are vital for pubertal development and reproduction. Arcuate nucleus Kiss1 (Kiss1ARH) neurons are responsible for the pulsatile release of Gonadotropin-releasing Hormone (GnRH). In females, the behavior of Kiss1ARH neurons, expressing Kiss1, Neurokinin B (NKB), and Dynorphin (Dyn), varies throughout the ovarian cycle. Studies indicate that 17{beta}-estradiol (E2) reduces peptide expression but increases Vglut2 mRNA and glutamate neurotransmission in these neurons, suggesting a shift from peptidergic to glutamatergic signaling. To investigate this shift, we combined transcriptomics, electrophysiology, and mathematical modeling. Our results demonstrate that E2 treatment upregulates the mRNA expression of voltage-activated calcium channels, elevating the whole-cell calcium current and that contribute to high-frequency burst firing. Additionally, E2 treatment decreased the mRNA levels of Canonical Transient Receptor Potential (TPRC) 5 and G protein-coupled K+ (GIRK) channels. When TRPC5 channels in Kiss1ARH neurons were deleted using CRISPR, the slow excitatory postsynaptic potential (sEPSP) was eliminated. Our data enabled us to formulate a biophysically realistic mathematical model of the Kiss1ARH neuron, suggesting that E2 modifies ionic conductances in Kiss1ARH neurons, enabling the transition from high frequency synchronous firing through NKB-driven activation of TRPC5 channels to a short bursting mode facilitating glutamate release. In a low E2 milieu, synchronous firing of Kiss1ARH neurons drives pulsatile release of GnRH, while the transition to burst firing with high, preovulatory levels of E2 would facilitate the GnRH surge through its glutamatergic synaptic connection to preoptic Kiss1 neurons.

neuroscience↗

bioRxiv2024

POMC neurons control fertility through differential signaling of MC4R in Kisspeptin neurons in the female mouse

Inactivating mutations in the melanocortin 4 receptor (MC4R) gene cause monogenic obesity. Interestingly, female patients also display various degrees of reproductive disorders, in line with the subfertile phenotype of MC4RKO female mice. However, the cellular mechanisms by which MC4R regulates reproduction are unknown. Kiss1 neurons directly stimulate gonadotropin-releasing hormone (GnRH) release through two distinct populations; the Kiss1ARH neurons, controlling GnRH pulses, and the sexually dimorphic Kiss1AVPV/PeN neurons controlling the preovulatory LH surge. Here, we show that Mc4r expressed in Kiss1 neurons regulates fertility in females. In vivo, deletion of Mc4r from Kiss1 neurons in female mice replicates the reproductive impairments of MC4RKO mice without inducing obesity. Conversely, reinsertion of Mc4r in Kiss1 neurons of MC4R null mice restores estrous cyclicity and LH pulsatility without reducing their obese phenotype. In vitro, we dissect the specific action of MC4R on Kiss1ARH vs Kiss1AVPV/PeN neurons and show that MC4R activation excites Kiss1ARH neurons through direct synaptic actions. In contrast, Kiss1AVPV/PeN neurons are normally inhibited by MC4R activation except under elevated estradiol levels, thus facilitating the activation of Kiss1AVPV/PeN neurons to induce the LH surge driving ovulation in females. Our findings demonstrate that POMCARH neurons acting through MC4R, directly regulate reproductive function in females by stimulating the "pulse generator" activity of Kiss1ARH neurons and restricting the activation of Kiss1AVPV/PeN neurons to the time of the estradiol-dependent LH surge, and thus unveil a novel pathway of the metabolic regulation of fertility by the melanocortin system.

neuroscience↗

bioRxiv2021

Sex-dependent development of Kras-induced anal squamous cell carcinoma in mice

Anal squamous cell carcinoma (SCC) will be diagnosed in an estimated 9,080 adults in the United States this year, and rates have been rising over the last several decades. Most people that develop anal SCC have associated human papillomavirus (HPV) infection ([~]85-95%), with approximately 5-15% of anal SCC cases occurring in HPV-negative patients from unknown etiology. This study identified and characterized a Kras-driven, female sex hormone-dependent development of anal squamous cell carcinoma (SCC) in the LSL-KrasG12D ; Pdx1-Cre (KC) mouse model that is not dependent on papillomavirus infection. One hundred percent of female KC mice develop anal SCC, while no male KC mice develop tumors. Both male and female KC anal tissue express Pdx1 and Cre-recombinase mRNA, and the activated mutant KrasG12D gene. Although the driver gene mutation KrasG12D is present in anus of both sexes, only female KC mice develop Kras-mutant induced anal SCC. To understand the sex-dependent differences, KC male mice were castrated and KC female mice were ovariectomized. Castrated KC males displayed an unchanged phenotype with no anal tumor formation. In contrast, ovariectomized KC females demonstrated a marked reduction in anal SCC development, with only 15% developing anal SCC. Finally, exogenous administration of estrogen rescued the tumor development in ovariectomized KC female mice and induced tumor development in castrated KC males. These results confirm that the anal SCC is estrogen mediated. The delineation of the role of female sex hormones in mediating mutant Kras to drive anal SCC pathogenesis highlights a subtype of anal SCC that is independent of papillomavirus infection. These findings may have clinical applicability for the papillomavirus-negative subset of anal SCC patients that typically respond poorly to standard of care chemoradiation.

cancer biology↗

bioRxiv2020

Insulin potentiates the synchronous firing of arcuate nucleus Kiss1 neurons that protects against diet-induced obesity

Kisspeptin (Kiss1) neurons are essential for reproduction, but their role in the control of energy balance and other homeostatic functions remains unclear. High frequency firing of hypothalamic arcuate Kiss1 (Kiss1ARH) neurons releases kisspeptin into the median eminence, and neurokinin B (NKB) and dynorphin onto neighboring Kiss1ARH neurons to generate a slow excitatory postsynaptic potential (EPSP) mediated by TRPC5 channels that entrains intermittent, synchronous firing of Kiss1ARH neurons. High frequency optogenetic stimulation of Kiss1ARH neurons releases glutamate to excite the anorexigenic proopiomelanocortin (POMC) neurons and inhibit the orexigenic neuropeptide Y/agouti-related peptide (AgRP) neurons via metabotropic glutamate receptors. At the molecular level, the endoplasmic reticulum calcium-sensing protein stromal interaction molecule 1 (STIM1) is critically involved in the regulation of neuronal Ca2+ signaling and neuronal excitability through its interaction with plasma membrane calcium (e.g., TRPC) channels. 17{beta}-estradiol (E2) downregulates Stim1 mRNA expression in female arcuate neurons. Therefore, we hypothesized that deletion of Stim1 in Kiss1ARH neurons would increase neuronal excitability and their synchronous firing, which ultimately would affect energy homeostasis. Using optogenetics in combination with whole-cell recording and GCaMP6 imaging in slices, we discovered that the deletion of Stim1 in Kiss1 neurons significantly increased the amplitude of the slow EPSP and augmented synchronous [Ca2+]i oscillations in Kiss1ARH neurons. Deletion of Stim1 in Kiss1ARH neurons amplified the actions of NKB and protected ovariectomized female mice from developing obesity and glucose intolerance with high-fat dieting. Therefore, STIM1 appears to play a critical role in regulating synchronous firing of Kiss1ARH neurons, which ultimately affects energy homeostasis. Significance StatementHypothalamic arcuate kisspeptin (Kiss1ARH) neurons are essential for stimulating the pulsatile release of gonadotropin releasing hormone (GnRH) and maintaining fertility. However, Kiss1ARH neurons appear to be a key player in coordinating energy balance with reproduction. The regulation of calcium channels and hence calcium signaling is critically dependent on the endoplasmic reticulum calcium-sensing protein stromal interaction molecule 1 (STIM1), which interacts with the plasma membrane calcium channels. We have conditionally deleted Stim1 in Kiss1ARH neurons and found that it significantly increased the excitability of Kiss1ARH neurons and protected ovariectomized female mice from developing obesity and glucose intolerance with high-fat dieting.

neuroscience↗