Neuropeptidomic Components Generated by Proteomic Functions in Secretory Vesicles for Cell–Cell Communication

Diverse neuropeptides participate in cell–cell communication to coordinate neuronal and endocrine regulation of physiological processes in health and disease. Neuropeptides are short peptides ranging in length from ~3 to 40 amino acid residues that are involved in biological functions of pain, stress, obesity, hypertension, mental disorders, cancer, and numerous health conditions. The unique neuropeptide sequences define their specific biological actions. Significantly, this review article discusses how the neuropeptide field is at the crest of expanding knowledge gained from mass-spectrometry-based neuropeptidomic studies, combined with proteomic analyses for understanding the biosynthesis of neuropeptidomes. The ongoing expansion in neuropeptide diversity lies in the unbiased and global mass-spectrometry-based approaches for identification and quantitation of peptides. Current mass spectrometry technology allows definition of neuropeptide amino acid sequence structures, profiling of multiple neuropeptides in normal and disease conditions, and quantitative peptide measures in biomarker applications to monitor therapeutic drug efficacies. Complementary proteomic studies of neuropeptide secretory vesicles provide valuable insight into the protein processes utilized for neuropeptide production, storage, and secretion. Furthermore, ongoing research in developing new computational tools will facilitate advancements in mass-spectrometry-based identification of small peptides. Knowledge of the entire repertoire of neuropeptides that regulate physiological systems will provide novel insight into regulatory mechanisms in health, disease, and therapeutics

V-ATPase-Mediated Granular Acidification Is Regulated by the V-ATPase Accessory Subunit Ac45 in POMC-Producing Cells

The regulation of the V-ATPase, the proton pump mediating intraorganellar acidification, is still elusive. We find that excess of the neuroendocrine V-ATPase accessory subunit Ac45 reduces the intragranular pH and consequently disturbs prohormone convertase activation and prohormone processing. Thus, Ac45 represents the first V-ATPase regulator

Spinal astrocytes produce and secrete dynorphin neuropeptides

a b s t r a c t Dynorphin peptide neurotransmitters (neuropeptides) have been implicated in spinal pain processing based on the observations that intrathecal delivery of dynorphin results in proalgesic effects and disruption of extracellular dynorphin activity (by antisera) prevents injury evoked hyperalgesia. However, the cellular source of secreted spinal dynorphin has been unknown. For this reason, this study investigated the expression and secretion of dynorphin-related neuropeptides from spinal astrocytes (rat) in primary culture. Dynorphin A (1-17), dynorphin B, and a-neoendorphin were found to be present in the astrocytes, illustrated by immunofluorescence confocal microscopy, in a discrete punctate pattern of cellular localization. Measurement of astrocyte cellular levels of these dynorphins by radioimmunoassays confirmed the expression of these three dynorphin-related neuropeptides. Notably, BzATP (3 0 -O-(4-benzoyl)benzoyl adenosine 5 0 -triphosphate) and KLA (di[3-deoxy-D-manno-octulosonyl]-lipid A) activation of purinergic and toll-like receptors, respectively, resulted in stimulated secretion of dynorphins A and B. However, a-neoendorphin secretion was not affected by BzATP or KLA. These findings suggest that dynorphins A and B undergo regulated secretion from spinal astrocytes. These findings also suggest that spinal astrocytes may provide secreted dynorphins that participate in spinal pain processing

A semaphorin code defines subpopulations of spinal motor neurons during mouse development

Abstract In the spinal cord, motor neurons (MNs) with similar muscle targets and sensory inputs are grouped together into motor pools. To date, relatively little is known about the molecular mechanisms that control the establishment of pool-specific circuitry. Semaphorins, a large family of secreted and cell surface proteins, are important mediators of developmental processes such as axon guidance and cell migration. Here, we used mRNA in situ hybridization to study the expression patterns of semaphorins and their receptors, neuropilins and plexins, in the embryonic mouse spinal cord. Our data show that semaphorins and their receptors are differentially expressed in MNs that lie in distinct locations within the spinal cord. Furthermore, we report a combinatorial expression of class 3 (secreted) semaphorins and their receptors that characterizes distinct motor pools within the brachial and lumbar spinal cord. Finally, we found that a secreted semaphorin, Sema3A, elicits differential collapse responses in topologically distinct subpopulations of spinal MNs. These findings lead us to propose that semaphorins and their receptors might play important roles in the sorting of motor pools and the patterning of their afferent and efferent projections

The opioid peptide beta-endorphin stimulates acrosome reaction in human spermatozoa

The acrosome reaction occurs in vivo following sperm capacitation and is essential for the acquisition of sperm fertilization ability. However, little is known about the molecular identity of the physiological acrosome reaction regulators. In addition to progesterone, which is produced by cumulus oophorus cells and known to regulate acrosome reaction by activating the specific calcium channel CatSper, endogenous opioid peptides such as beta-endorphin and met-enkephalin are present at high concentrations in the follicular fluid suggesting that the opioid system may be involved in the mechanisms regulating the acrosome reaction in humans. By using Reverse Transcription-PCR, western blot and immunofluorescence approaches, we described the presence and localization of the beta-endorphin precursor, pro-opiomelanocortinin the middle section and in flagellum of human spermatozoa, and inside the seminiferous tubules of human testis. Flow cytometry and intracellular calcium analyses showed that beta-endorphin causes an inversely dose-dependent increase in the percentage of acrosome-reacted sperm cells by a calcium-independent protein kinase C pathway. These findings are important for future studies of sperm physiology and provide new insight into the function of the opioid system as a target of fertility management.Peer Reviewe

Human iPSC neurons display activity-dependent neurotransmitter secretion: aberrant catecholamine levels in schizophrenia neurons.

This study investigated human-induced pluripotent stem cell (hiPSC) -derived neurons for their ability to secrete neurotransmitters in an activity-dependent manner, the fundamental property required for chemical neurotransmission. Cultured hiPSC neurons showed KCl stimulation of activity-dependent secretion of catecholamines--dopamine (DA), norepinephrine (NE), and epinephrine (Epi)--and the peptide neurotransmitters dynorphin and enkephlain. hiPSC neurons express the biosynthetic enzymes for catecholamines and neuropeptides. Because altered neurotransmission contributes to schizophrenia (SZ), we compared SZ to control cultures of hiPSC neurons and found that SZ cases showed elevated levels of secreted DA, NE, and Epi. Consistent with increased catecholamines, the SZ neuronal cultures showed a higher percentage of tyrosine hydroxylase (TH)-positive neurons, the first enzymatic step for catecholamine biosynthesis. These findings show that hiPSC neurons possess the fundamental property of activity-dependent neurotransmitter secretion and can be advantageously utilized to examine regulation of neurotransmitter release related to brain disorders

Human iPSC neurons display activity-dependent neurotransmitter secretion: aberrant catecholamine levels in schizophrenia neurons.

This study investigated human-induced pluripotent stem cell (hiPSC) -derived neurons for their ability to secrete neurotransmitters in an activity-dependent manner, the fundamental property required for chemical neurotransmission. Cultured hiPSC neurons showed KCl stimulation of activity-dependent secretion of catecholamines--dopamine (DA), norepinephrine (NE), and epinephrine (Epi)--and the peptide neurotransmitters dynorphin and enkephlain. hiPSC neurons express the biosynthetic enzymes for catecholamines and neuropeptides. Because altered neurotransmission contributes to schizophrenia (SZ), we compared SZ to control cultures of hiPSC neurons and found that SZ cases showed elevated levels of secreted DA, NE, and Epi. Consistent with increased catecholamines, the SZ neuronal cultures showed a higher percentage of tyrosine hydroxylase (TH)-positive neurons, the first enzymatic step for catecholamine biosynthesis. These findings show that hiPSC neurons possess the fundamental property of activity-dependent neurotransmitter secretion and can be advantageously utilized to examine regulation of neurotransmitter release related to brain disorders