Opioid receptor modulation of mossy fiber synaptogenesis: independence from long-term potentiation

Escobar, Martha L.; Barea-Rodrı́guez, Edwin J.; Derrick, Brian E.; Reyes, Joe A; Martinez, Joe L.

doi:10.1016/s0006-8993(96)01373-x

Cited by 40 publications

(46 citation statements)

References 24 publications

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“…Given the limitations of morphological analyses, we cannot entirely exclude the possibility that minor cell loss had escaped detection (e.g., Sutula et al, 1988;Cavazos and Sutula, 1990). However, an alternative explanation is provided by recent studies demonstrating that mossy fiber sprouting does not always require neuronal degeneration (Stringer et al, 1997;Holmes et al, 1998), but can also result from continuous neuronal activation (Adams et al, 1997;Escobar et al, 1997;Hassan et al, 2000). The protracted time course of the mossy fiber sprouting after experimental febrile seizures suggests that the mechanisms involved might be chronic: the pattern observed here was that of a slow increase of mossy fibers in GC layer and ML.…”

Section: Discussionmentioning

confidence: 97%

Mossy fiber plasticity and enhanced hippocampal excitability, without hippocampal cell loss or altered neurogenesis, in an animal model of prolonged febrile seizures

et al. 2003

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Seizures induced by fever (febrile seizures) are the most frequent seizures affecting infants and children; however, their impact on the developing hippocampal formation is not completely understood. Such understanding is highly important because of the potential relationship of prolonged febrile seizures to temporal lobe epilepsy. Using an immature rat model, we have previously demonstrated that prolonged experimental febrile seizures render the hippocampus hyperexcitable throughout life. Here we examined whether (1) neuronal loss, (2) altered neurogenesis, or (3) mossy fiber sprouting, all implicated in epileptogenesis in both animal models and humans, were involved in the generation of a pro-epileptic, hyperexcitable hippocampus by these seizures. The results demonstrated that prolonged experimental febrile seizures did not result in appreciable loss of any vulnerable hippocampal cell population, though causing strikingly enhanced sensitivity to hippocampal excitants later in life. In addition, experimental febrile seizures on postnatal day 10 did not enhance proliferation of granule cells, whereas seizures generated by kainic acid during the same developmental age increased neurogenesis in the immature hippocampus. However, prolonged febrile seizures resulted in long-term axonal reorganization in the immature hippocampal formation: Mossy fiber densities in granule cell-and molecular layers were significantly increased by 3 months (but not 10 days) after the seizures. Thus, the data indicate that prolonged febrile seizures influence connectivity of the immature hippocampus long-term, and this process requires neither significant neuronal loss nor altered neurogenesis. In addition, the temporal course of the augmented mossy fiber invasion of the granule cell and molecular layers suggests that it is a consequence, rather than the cause, of the hyperexcitable hippocampal network resulting from these seizures.

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Section: Discussionmentioning

confidence: 97%

Mossy fiber plasticity and enhanced hippocampal excitability, without hippocampal cell loss or altered neurogenesis, in an animal model of prolonged febrile seizures

et al. 2003

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“…The function of olfactory bulb enkephalin is not clear; in other regions enkephalin has a role in analgesia and the reward pathways (36). Additional roles for enkephalin include synaptogenesis and neurite outgrowth (42,43), and it is possible that olfactory bulb enkephalin is involved in this function.…”

Section: Discussionmentioning

confidence: 99%

Characterization of Carboxypeptidase A6, an Extracellular Matrix Peptidase

Lyons

Callaway

Fricker

2008

Journal of Biological Chemistry

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Carboxypeptidase A6 (CPA6) is a member of the M14 metallocarboxypeptidase family that is highly expressed in the adult mouse olfactory bulb and broadly expressed in embryonic brain and other tissues. A disruption in the human CPA6 gene is linked to Duane syndrome, a defect in the abducens nerve/lateral rectus muscle connection. In this study the cellular distribution, processing, and substrate specificity of human CPA6 were investigated. The 50-kDa pro-CPA6 is routed through the constitutive secretory pathway, processed by furin or a furinlike enzyme into the 37-kDa active form, and secreted into the extracellular matrix. CPA6 cleaves the C-terminal residue from a range of substrates, including small synthetic substrates, larger peptides, and proteins. CPA6 has a preference for large hydrophobic C-terminal amino acids as well as histidine. Peptides with a penultimate glycine or proline are very poorly cleaved. Several neuropeptides were found to be processed by CPA6, including Met-and Leu-enkephalin, angiotensin I, and neurotensin. Whereas CPA6 converts enkephalin and neurotensin into forms known to be inactive toward their receptors, CPA6 converts inactive angiotensin I into the biologically active angiotensin II. Taken together, these data suggest a role for CPA6 in the regulation of neuropeptides in the extracellular environment within the olfactory bulb and other parts of the brain.

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“…The cleavage performed by CPA4 would eliminate the binding of these peptides to their receptors. Although enkephalin is a well known neuropeptide that functions in analgesia and the reward pathway, additional roles for enkephalin include synaptogenesis and neurite outgrowth (43,44). Some granin-derived peptides have been postulated to participate as regulators of tissue repair, inflammatory reaction, and innate immunity (45).…”

Section: Table 5 Products Of Cpa4mentioning

confidence: 99%

Characterization of the Substrate Specificity of Human Carboxypeptidase A4 and Implications for a Role in Extracellular Peptide Processing

Tanco

Zhang

Morano

et al. 2010

Journal of Biological Chemistry

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CPA4 (carboxypeptidase A4) is a member of the metallocarboxypeptidase family. CPA4 was originally found in a screen of mRNAs up-regulated by sodium butyrate-induced differentiation of cancer cells. Further studies suggested a relation between CPA4 and prostate cancer aggressiveness. In the present study, we determined that CPA4 is secreted from cells as a soluble proenzyme (pro-CPA4) that can be activated by endoproteases, such as trypsin. Three complementary approaches were used to study the substrate specificity of CPA4; kinetic analysis was performed using a new series of chromogenic substrates and some biologically relevant peptides, the cleavage of synthetic peptides was tested individually, and the cleavage of a mixture of >100 mouse brain peptides was examined using a quantitative peptidomics mass spectrometry-based approach. CPA4 was able to cleave hydrophobic C-terminal residues with a preference for Phe, Leu, Ile, Met, Tyr, and Val. However, not all peptides with C-terminal hydrophobic residues were cleaved, indicating the importance of additional residues within the peptide. Aliphatic, aromatic, and basic residues in the P1 position have a positive influence on the cleavage specificity. In contrast, acidic residues, Pro, and Gly have a negative influence in the P1 position. Some of the peptides identified as CPA4 substrates (such as neurotensin, granins, and opioid peptides) have been previously shown to function in cell proliferation and differentiation, potentially explaining the link between CPA4 and cancer aggressiveness. Taken together, these studies suggest that CPA4 functions in neuropeptide processing and regulation in the extracellular environment. Carboxypeptidases (CPs)3 hydrolyze a single amino acid from the C terminus of peptides and proteins. Metallo-CPs use a catalytic mechanism in which nucleophilic attack on a peptide bond is mediated by a Zn 2ϩ -activated water molecule (1). Most metallo-CPs are classified based on amino acid sequence, structure, and function into subfamilies within clan MC, family M14 (2). These subfamilies include M14A, also known as the CPA/ CPB subfamily; M14B, also known as the CPN/CPE subfamily; M14C, which includes ␥-D-glutamyl-(L)-meso-diaminopimelate peptidase I from Bacillus sphaericus; and a proposed fourth subfamily, including cytosolic CPs (3, 4). Metallo-CPs have also been divided into subgroups based on substrate specificity: A-like enzymes with preference for hydrophobic C-terminal amino acids; B-like enzymes, which cleave C-terminal basic residues; CPs with preference for glutamate in the C-terminal position; and CPs with a broad substrate specificity.CPA4 (carboxypeptidase A4) belongs to the M14A subfamily of carboxypeptidases. The pancreatic members of this subfamily (CPA1, CPA2, and CPB) act in the degradation of dietary proteins in the digestive tract. Other members of this subfamily display a wide spectrum of physiological roles. Mast cell carboxypeptidase (recently renamed CPA3) is found in the secretory granules of mast cells and plays a role ...

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Opioid receptor modulation of mossy fiber synaptogenesis: independence from long-term potentiation

Cited by 40 publications

References 24 publications

Mossy fiber plasticity and enhanced hippocampal excitability, without hippocampal cell loss or altered neurogenesis, in an animal model of prolonged febrile seizures

Mossy fiber plasticity and enhanced hippocampal excitability, without hippocampal cell loss or altered neurogenesis, in an animal model of prolonged febrile seizures

Characterization of Carboxypeptidase A6, an Extracellular Matrix Peptidase

Characterization of the Substrate Specificity of Human Carboxypeptidase A4 and Implications for a Role in Extracellular Peptide Processing

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