Disease relevance of CPE

• When either virus obtained from CPE(surv) cells that had spontaneously lost the sg RNA or virus from which defective particles had been removed was used to establish persistently infected cells, these cells were also protected from the CPE after superinfection with cp CSFV [1].
• However, when naive cells were infected with supernatants from CPE(surv)cells that contained defective virus particles, the CPE reappeared within three to five virus passages, indicating that the sg RNA retained its cytopathogenic potential [1].
• Bovine enterovirus CPE at different multiplicities of infection in the absence of viral RNA synthesis [2].
• Moreover, the rIFN-as could inhibit infectious bovine rhinotracheitis virus replication in the MDBK cell line using CPE inhibition method [3].
• Enkephalin convertase demonstrated in the pituitary and adrenal gland by [3H]guanidinoethylmercaptosuccinic acid autoradiography: dehydration decreases neurohypophyseal levels [4].

High impact information on CPE

• Within the secretory granules, carboxypeptidase E (CPE) activity is found in both a soluble and a membrane-bound form, which differ slightly in relative molecular mass (Mr) [5].
• Here, to investigate whether the CPE activities in the various tissues are produced from a single gene, purified CPE was partially sequenced and oligonucleotide probes were used to isolate a clone encoding CPE from a bovine pituitary complementary DNA library [5].
• The predicted amino-acid sequence of the cDNA clone contains the partially determined sequences of CPE, several pairs of basic amino acids and displays some homology with both carboxypeptidases A and B. Restriction analysis of bovine genomic DNA suggests only one gene for CPE [5].
• Carboxypeptidase E (enkephalin convertase) was first identified as the carboxypeptidase B-like enzyme involved in the biosynthesis of enkephalin in bovine adrenal chromaffin granules [5].
• These results support the hypothesis that pro-CPH is processed and activated during axonal transport from neuronal perikarya of SON to nerve terminals of the posterior pituitary [6].

Chemical compound and disease context of CPE

• The level of anterior pituitary enkephalin convertase is unchanged by dehydration, adrenalectomy, or dexamethasone or in Brattleboro rats [4].

Biological context of CPE

• N-POMC when added to the assays did not inhibit the aggregation of CPE with prolactin or insulin, indicating that these interactions do not involve a binding site for N-POMC [7].
• To further explore the possibility that CPE serves to mediate the association of content proteins with the membrane during granule biogenesis, the binding of CPE to granule content proteins was investigated using an in vitro aggregation assay in which the selective precipitation of granule content proteins is induced by titration of the pH to <6 [7].
• Pro-insulin bound CPE with similar kinetics [8].
• Pro-enkephalin, but not CGA bound to CPE with similar IC50 as pro-insulin and N-POMC1-26 [8].
• Subcultivation of the persistently infected cultures led to virus replication followed by CPE and then cell regrowth [9].

Anatomical context of CPE

• Synthetic COOH-terminal peptides 11-24 residues in length are able to bind to bovine pituitary membranes and can be extracted by conditions that extract the membrane-bound form of CPE [10].
• Taken together, these results are consistent with a model in which the decreasing pH and increasing Ca2+ levels in the trans Golgi network induce the aggregation of CPE, which contributes to the sorting of this protein into regulated pathway secretory vesicles [11].
• The mouse anterior pituitary-derived cell line AtT-20 has been widely used to study the biosynthesis and secretion of peptide hormones, such as ACTH, and peptide-processing enzymes, such as carboxypeptidase-E (CPE) [12].
• Applications of this rapid and sensitive radiometric assay to detect CPE in cultured cells and in subcellular fractions of the pituitary are described [13].
• This study evaluated the attachment, chemoattractive, proliferative and mineralization inductive potential of a bovine cementum extract (CPE) on newborn murine dental follicle cells (MDFC) in vitro [14].

Associations of CPE with chemical compounds

• The aggregation of M2-CPE does not explain the apparent membrane binding of this protein since the aggregate is solubilized by 1% Triton X-100 at pH 5.5 or by pH 6.0, whereas M2-CPE is not extracted from membranes under these conditions [11].
• Also, CPD does not elute from a substrate affinity column when the pH is raised to 8, which elutes CPE, although CPD can subsequently be eluted by arginine [15].
• Cholesterol depletion resulted in dissociation of CPE from secretory granule membranes and decreased the binding of prohormones to membranes [16].
• In vivo cholesterol depletion using lovastatin resulted in the lack of sorting of CPE and its cargo to the regulated secretory pathway [16].
• Both the 21-residue COOH-terminal peptide and the purified membrane form of CPE, but not the soluble form, partition into Triton X-114 only at low pH (pH less than 6) [10].

Physical interactions of CPE

• CPE has been shown to bind to an amino-terminal peptide of pro-opiomelanocortin (N-POMC) at pH 5.5 and hypothesized to be critically involved in the targeting of hormones such as POMC to the regulated secretory pathway [Cool, D. R., Normant, E., Shen, F., Chen, H. C., Pannell, L., Zhang, Y., and Loh, Y. P. (1997) Cell 88, 73-83] [7].
• In addition, CPE co-precipitated at pH 5.8 with purified prolactin and with insulin, which homophillically self-aggregate yet are structurally distinct from N-POMC [7].

Other interactions of CPE

• N-POMC1-26, which contains the POMC sorting signal, bound to CPE in the SG membranes with low affinity and the binding was ion independent [8].
• Carboxypeptidase E is a member of the carboxypeptidase A and B gene family, with many of the putative active-site and substrate-binding residues conserved between these enzymes [17].

Analytical, diagnostic and therapeutic context of CPE

• Cloning and sequence analysis of cDNA for bovine carboxypeptidase E [5].
• Of a range of cell cultures tested, the virus grew in secondary bovine kidney and MDBK cells, but consistently produced a CPE only in MDBK cells [18].
• The results were compared with those obtained with the conventional microtitre neutralization test (MNT) based on CPE reading [19].
• [3H] GEMSA binding activity is found only in fractions containing enkephalin convertase during enzyme purification from bovine pituitary by L-arginine affinity chromatography [20].
• Two-dimensional SDS-PAGE revealed that the poly(N-acetyllactosaminyl) oligosaccharides are predominantly present in glycoprotein IV, together with lesser labeling of glycoproteins II and III, whereas they are absent from dopamine beta-hydroxylase and carboxypeptidase H, which are the major glycoproteins of chromaffin granule membranes [21].

References