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  • Author: M. G. Castro x
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Biosynthesis of corticotrophin-releasing hormone (CRH) in mouse corticotrophic tumour cells expressing the human proCRH gene: intracellular storage and regulated secretion

M. G. Castro, J. Brooke, A. Bullman, M. Hannah, B. P. Glynn, and P. J. Lowry

ABSTRACT

The mouse corticotrophic tumour cell line AtT-20 naturally synthesizes pro-opiomelanocortin (POMC) which is proteolytically processed to N-POMC(1–76), ACTH, β-lipotrophin and β-endorphin. The processed products are stored in secretory vesicles and released upon stimulation with specific secretagogues. ArT-20 cells which have been stably transfected with the human corticotrophin-releasing hormone (CRH) gene store and secrete immunoreactive CRH. The present results demonstrate that the CRH precursor is proteolytically processed in the transfected cells to yield the 41 amino acid neuropeptide CRH(1–41). On stimulation with the secretagogue noradrenaline, CRH(1–41) was released into the medium, while the precursor was not. Whilst treatment of wild-type ArT-20 cells with exogenous CRH(1–41) (1 nm) caused a fourfold stimulation of ACTH release above basal levels, the peptide had no effect on ACTH release from the stably transfected cells R1 and R4. These results suggest that the endogenous CRH produced by the transfected R1 and R4 cells may cause down-regulation of their CRH receptors, and thus exogenous CRH cannot cause further stimulation of ACTH release in these cells. We propose that the CRH precursor is correctly processed in the transfected AtT-20 cells (R1 and R4) and that the foreign prohormone is sorted into the secretory pathway.

DOI:
https://doi.org/10.1677/jme.0.0070097
Volume 7: Issue 2,
Pages:
97–104 (8 total)
Restricted access

The use of inclusion bodies, isolated from Escherichia coli expressing corticotrophin-releasing hormone precursor, to raise specific antibodies against the neuropeptide moiety

M. G. Castro, P. R. Lowenstein, P. W. Saphier, E. A. Linton, and P. J. Lowry

ABSTRACT

We have expressed human pre-procorticotrophin-releasing hormone (pre-proCRH) as a fusion protein to β-galactosidase in Escherichia coli. The chimeric fusion protein was found in insoluble bacterial inclusion bodies. The inclusion bodies were isolated, purified and solubilized, and used as imunogens in rabbits to raise antibodies against the neuropeptide moiety. The antibodies generated were characterized by immunoassays and immunocytochemical techniques. The immunoassay results showed that the recombinant pre-proCRH antibodies cross-reacted with the full-length CRH precursor and several cleavage products derived from it, i.e. CRH(1–41) and CRH(36–41). They did not cross-react with the CRH antagonist CRH(9–41). Extracts of stalk median eminence from various species were also studied. The antibodies cross-reacted with extracts from ovine, bovine, human and rat tissues, exhibiting parallel displacement curves to that of synthetic rat/human CRH(1–41) used as standard. They also cross-reacted with a skin extract of the frog, a species known to contain a CRH-related peptide, i.e. sauvagine, in this tissue. The immunocytochemical studies demonstrated that the antibodies generated against recombinant human preproCRH labelled neurones in the rat paraventricular nucleus of the hypothalamus. They exhibited the same pattern of staining as that obtained with an antibody generated against synthetic CRH(1–41). The results indicate that these antibodies can recognize CRH(1–41) or CRH-related molecules in the hypothalamus in situ as well as in tissue extracts from several species. Hence, they will be useful tools in the study of the CRH biosynthetic pathway and its intracellular compartmentalization.

DOI:
https://doi.org/10.1677/jme.0.0050221
Volume 5: Issue 3,
Pages:
221–230 (10 total)
Restricted access

Presence of pro-vasopressin mRNA, neurophysin and arginine vasopressin in mouse anterior pituitary cells and the AtT-20 corticotrophic tumour cell line

Y. P. Loh, M. G. Castro, F.-J. Zeng, and U. Patel-Vaidya

ABSTRACT

Pro-vasopressin mRNA, neurophysin and arginine vasopressin (AVP) were assayed in the mouse anterior pituitary gland, in mouse anterior pituitary cells in culture and in the AtT-20 corticotrophic tumour cell line. Northern blot analysis revealed the presence of an ∼700 base pair pro-vasopressin mRNA in anterior pituitary and AtT-20 cells. Neurophysin, identified by immunoblots, and AVP, identified by high-performance liquid chromatography and cross-reactivity with AVP antiserum, were detected in anterior pituitary cells and AtT-20 cells. Immunocytochemical staining with anti-neurophysin showed that ∼40–45% of the dissociated anterior pituitary cells in culture and >95% of the AtT-20 cells were stained. Anterior pituitary cells in culture and AtT-20 cells had a basal level of release of AVP in the 0·01–0·1 nm range. These results indicate that anterior pituitary cells and AtT-20 cells have the ability to synthesize and process pro-vasopressin to AVP and neurophysin, endogenously.

DOI:
https://doi.org/10.1677/jme.0.0010039
Volume 1: Issue 1,
Pages:
39–48 (10 total)
Free access

Breast adipose regulation of premenopausal breast epithelial phenotype involves interleukin 10

Iad Alhallak, Keith G Wolter, Ana Castro Munoz, Frank A Simmen, Richard J Ward, Stacy A Petty, Lin-Xi Li, and Rosalia C M Simmen

Epidemiological studies inversely associate BMI with breast cancer risk in premenopausal women, but the pathophysiological linkage remains ill-defined. Despite the documented relevance of the ‘local’ environment to breast cancer progression and the well-accepted differences in transcriptome and metabolic properties of anatomically distinct fat depots, specific breast adipose contributions to the proliferative potential of non-diseased breast glandular compartment are not fully understood. To address early breast cancer causation in the context of obesity status, we compared the cellular and molecular phenotypes of breast adipose and matched breast glandular tissue from premenopausal non-obese (mean BMI = 27 kg/m2) and obese (mean BMI = 44 kg/m2) women. Breast adipose from obese women showed higher expression levels of adipogenic, pro-inflammatory, and estrogen synthetic genes than from non-obese women. Obese breast glandular tissue displayed lower proliferation and inflammatory status and higher expression of anti-proliferative/pro-senescence biomarkers TP53 and p21 than from non-obese women. Transcript levels for T-cell receptor and co-receptors CD3 and CD4 were higher in breast adipose of obese cohorts, coincident with elevated adipose interleukin 10 (IL10) and FOXP3 gene expression. In human breast epithelial cell lines MCF10A and HMEC, recombinant human IL10 reduced cell viability and CCND1 transcript levels, increased those of TP53 and p21, and promoted (MCF10A) apoptosis. Our findings suggest that breast adipose-associated IL10 may mediate paracrine interactions between non-diseased breast adipose and breast glandular compartments and highlight how breast adipose may program the local inflammatory milieu, partly by recruiting FOXP3+ T regulatory cells, to influence premenopausal breast cancer risk.

DOI:
https://doi.org/10.1530/JME-21-0100
Volume 67: Issue 4,
Pages:
173–188 (16 total)