CARBOXYPEPTIDASE E (CPE) is a prohormone processing exopeptidase and a prohormone sorting receptor for the regulated secretory pathway (RSP) in endocrine and neuroendocrine cells (1, 2, 3, 4). Peptide hormones and neuropeptides are synthesized as larger precursors that are first cleaved by prohormone convertases, either in between or on the carboxyl side of paired basic residues to yield basic residue-extended peptides (5, 6, 7). Within secretory granules of the RSP, CPE then cleaves the basic residues from these hormone and neuropeptide intermediates to generate bioactive peptides.
NCBI Summary:
Carboxypeptidase E cleaves C-terminal amino acid residues and is involved in neuropeptide processing. It is a peripheral membrane protein. CPE specifically binds regulated secretory pathway proteins, including prohormones, but not constitutively secreted proteins.
Sasson R, et al 2003 reported novel genes modulated by FSH in normal and immortalized FSH-responsive
cells and new insights into the mechanism of FSH action.
Follicle-stimulating hormone (FSH) controls the development of follicle-enclosed oocytes in the
mammalian ovary by interacting with specific receptors located exclusively on granulosa cells. Its
biological activity involves stimulation of intercellular communication, intracellular signaling, and
up-regulation of steroidogenesis; the entire spectrum of genes regulated by FSH is not yet fully
characterized. The authors have established monoclonal rat FSH-responsive granulosa cell lines that
express FSH receptors at 20-fold higher rates than with primary cells, and thus increased the
probability of yielding a distinct spectrum of genes modulated by FSH. Using Affymetrix DNA
microarrays, they discovered 11 genes not reported earlier to be up-regulated by FSH and 9 genes
not reported earlier to be down-regulated by FSH. Modulation of signal transduction associated
with G-protein signaling, phosphorylation of proteins, and intracellular-extracellular ion balance
was suggested by up-regulation of decay accelerating factor GPI-form precursor (DAF), membrane
interacting protein RGS16, protein tyrosine phosphatase (PTPase), oxidative stress-inducible protein tyrosine phosphatase (OSIPTPase), and down-regulation of rat prostatic acid phosphatase
(rPAP), Na+, K+-ATPase, and protein phosphatase 1beta. Elevation in granzyme-like proteins 1
and 3, and natural killer (NK) cell protease 1 (NKP-1) along with reduction in carboxypeptidase E
indicates possible FSH-mediated preparation of the cells for apoptosis.
Follicle stages
Comment
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: subfertile Comment: The carboxypeptidase E knockout mouse exhibits endocrinological and behavioral deficits Cawley NX, et al .
A carboxypeptidase E (CPE) knockout (KO) mouse was generated by deletion of exons 4 and 5 from the CPE gene, and its phenotype was characterized. KO mice became obese by 10-12 wk of age and reached 60-80 g by 40 wk. At this age, body fat content was more than double that in the wild-type (WT) controls. The null animals consumed more food overall, were less physically active during the light phase of the light-dark cycle, and burned fewer calories as fat than WT littermates. Fasting levels of glucose and insulin-like immunoreactivity in plasma were elevated in both male and female KO mice at approximately 20 wk; males recovered fully and females partially from this state by 32 wk. At this time, insulin-like immunoreactivity in the plasma, identified as proinsulin, was 50-100 times higher than that of the WT animals. The KO mice showed impaired glucose clearance and were insulin resistant. High levels of leptin and no circulating fully processed cocaine- and amphetamine-related transcript, a peptide that is responsive to leptin-induced feedback inhibition of feeding, were found in serum. The KO mice were subfertile and showed deficits in GnRH processing in the hypothalamus. Behavioral analyses revealed that KO animals showed diminished reactivity to stimuli and had reduced muscle strength and coordination, as well as visual placing and toe-pinch reflexes. These data demonstrate that CPE KO mice display a wide range of neural and endocrine abnormalities and suggest that CPE may have additional physiological roles beyond those ascribed to peptide processing and sorting of prohormones in cells.