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Olfactory marker protein is unlikely to be cleaved by calpain 5.

ABSTRACT: Olfactory maturation marker protein (OMP) is expressed in olfactory receptor neurons and hypothalamic neurons. OMP is a nested gene located in the intron of calpain 5 (CAPN5), a Ca²⁺-dependent cysteine protease. Despite being located at the same genomic locus, genetic regulation of the reciprocal expression of OMP and CAPN5 has been suggested. By performing a motif search, we detected possible calpain cleavage sites in OMP. However, the direct proteolytic regulation of OMP by CAPN5 is unclear. Here, we generated OMP fused with Myc-tag and His-tag at its N- and C-termini and examined whether CAPN5 cleaves OMP into fragments by detecting immunoreactivity against Myc, OMP and His. Western blotting demonstrated that OMP was unlikely to be cleaved even in the presence of Ca²⁺ in vitro. We expressed OMP and CAPN5 in HEK293T cells and applied a calcium ionophore under physiological conditions in cellulo, which resulted in no apparent fragmentation of OMP. We also applied liquid chromatography/mass spectrometry to the electrophoresed fractions smaller than the uncut Myc-OMP-His signals, which demonstrated no significant fragmentation of OMP. These results collectively indicate that OMP is unlikely to be cleaved by CAPN5.

SUBMITTER: Nakashima N

PROVIDER: S-EPMC9618205 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature

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Olfactory marker protein is unlikely to be cleaved by calpain 5.

Nakashima Noriyuki N Nakashima Kie K Nakashima Akiko A Takano Makoto M

Molecular brain 20221029 1

Olfactory maturation marker protein (OMP) is expressed in olfactory receptor neurons and hypothalamic neurons. OMP is a nested gene located in the intron of calpain 5 (CAPN5), a Ca<sup>2+</sup>-dependent cysteine protease. Despite being located at the same genomic locus, genetic regulation of the reciprocal expression of OMP and CAPN5 has been suggested. By performing a motif search, we detected possible calpain cleavage sites in OMP. However, the direct proteolytic regulation of OMP by CAPN5 is ...[more]

PMID: 36309704

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Project description:Olfactory receptor (OR)-associated events are mediated by well-conserved components in the olfactory epithelium, including olfactory G-protein (Golf), adenylate cyclase III (ACIII), and olfactory marker protein (OMP). The expression of ORs has recently been observed in non-olfactory tissues where they are involved in monitoring extracellular chemical cues. The large number of OR genes and their sequence similarities illustrate the need to find an effective and simple way to detect non-olfactory OR-associated events. In addition, expression profiles and physiological functions of ORs in non-olfactory tissues are largely unknown. To overcome limitations associated with using OR as a target protein, this study used OMP with Golf and ACIII as targets to screen for potential OR-mediated sensing systems in non-olfactory tissues. Here, we show using western blotting, real-time PCR, and single as well as double immunoassays that ORs and OR-associated proteins are co-expressed in diverse tissues. The results of immunohistochemical analyses showed OMP (+) cells in mouse heart and in the following cells using the corresponding marker proteins c-kit, keratin 14, calcitonin, and GFAP in mouse tissues: interstitial cells of Cajal of the bladder, medullary thymic epithelial cells of the thymus, parafollicular cells of the thyroid, and Leydig cells of the testis. The expression of ORs in OMP (+) tissues was analyzed using a refined microarray analysis and validated with RT-PCR and real-time PCR. Three ORs (olfr544, olfr558, and olfr1386) were expressed in the OMP (+) cells of the bladder and thyroid as shown using a co-immunostaining method. Together, these results suggest that OMP is involved in the OR-mediated signal transduction cascade with olfactory canonical signaling components between the nervous and endocrine systems. The results further demonstrate that OMP immunohistochemical analysis is a useful tool for identifying expression of ORs, suggesting OMP expression is an indicator of potential OR-mediated chemoreception in non-olfactory systems.

Project description:BackgroundWhole genome duplications (WGDs) have been proposed to have made a significant impact on vertebrate evolution. Two rounds of WGD (1R and 2R) occurred in the common ancestor of Gnathostomata and Cyclostomata, followed by the third-round WGD (3R) in a common ancestor of all modern teleosts. The 3R-derived paralogs are good models for understanding the evolution of genes after WGD, which have the potential to facilitate phenotypic diversification. However, the recent studies of 3R-derived paralogs tend to be based on in silico analyses. Here we analyzed the paralogs encoding teleost olfactory marker protein (OMP), which was shown to be specifically expressed in mature olfactory sensory neurons and is expected to be involved in olfactory transduction.ResultsOur genome database search identified two OMPs (OMP1 and OMP2) in teleosts, whereas only one was present in other vertebrates. Phylogenetic and synteny analyses suggested that OMP1 and 2 were derived from 3R. Both OMPs showed distinct expression patterns in zebrafish; OMP1 was expressed in the deep layer of the olfactory epithelium (OE), which is consistent with previous studies of mice and zebrafish, whereas OMP2 was sporadically expressed in the superficial layer. Interestingly, OMP2 was expressed in a very restricted region of the retina as well as in the OE. In addition, the analysis of transcriptome data of spotted gar, a non-teleost fish, revealed that single OMP gene was expressed in the eyes.ConclusionWe found distinct expression patterns of zebrafish OMP1 and 2 at the tissue and cellular level. These differences in expression patterns may be explained by subfunctionalization as the model of molecular evolution. Namely, single OMP gene was speculated to be originally expressed in the OE and the eyes in the common ancestor of all Osteichthyes (bony fish including tetrapods). Then, two OMP gene paralogs derived from 3R-WGD reduced and specialized the expression patterns. This study provides a good example for analyzing a functional subdivision of the teleost OE and eyes as revealed by 3R-derived paralogs of OMPs.

Project description:The transcription factor E2F1 activates gene targets required for G1 -S phase progression and for apoptosis, and exhibits increased expression levels in neurons in several CNS diseases including HIV encephalitis, Alzheimer disease, and Parkinson's Disease. While E2F1 is known to regulate cell viability through activation of caspases, here we present evidence supporting the involvement of E2F1 in N-methyl-d-aspartate (NMDA) receptor-dependent, HIV-induced neuronal death mediated by calpains. Using an in vitro model of HIV-induced neurotoxicity that is dependent on NMDA receptor and calpain activation, we have shown that cortical neurons lacking functional E2F1 are less susceptible to neuronal death. In addition, we report that neuronal E2F1 is cleaved by calpain to a stable 55-kiloDalton fragment following NR2B-dependent NMDA receptor stimulation. This cleavage of E2F1 is protein conformation-dependent and involves at least two cleavage events, one at each terminus of the protein. Intriguingly, the stabilized E2F1 cleavage product is produced in post-mitotic neurons of all ages, but fails to be stabilized in cycling cells. Finally, we show that a matching E2F1 cleavage product is produced in human fetal neurons, suggesting that calpain cleavage of E2F1 may be produced in human cortical tissue. These results suggest neuronal E2F1 is processed in a novel manner in response to NMDA receptor-mediated toxicity, a mechanism implicated in HIV-associated neurocognitive disorders pathogenesis as well as several other diseases of the CNS. After crossing the blood-brain barrier, HIV-infected monocytes differentiate into macrophages and release excitotoxins and inflammatory factors including glutamate into the brain parenchyma (1). These factors stimulate neuronal N-Methyl-d-aspartate (NMDA) receptors (2), causing calcium influx (3) and subsequent activation of the cysteine protease calpain (4). Activated calpain cleaves multiple substrates including E2F1, producing a stabilized protein fragment with truncations at the N- and C-terminus (5). Calpain-cleaved E2F1 may contribute to calpain-mediated neuronal damage observed in NMDA receptor-mediated neurotoxicity (6).

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Olfactory marker protein is unlikely to be cleaved by calpain 5.

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Olfactory marker protein is unlikely to be cleaved by calpain 5.

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