Procorticotrophin-releasing hormone: endoproteolytic processing and differential release of its derived peptides within stably transfected AtT20 cells

PERONE, MJ; MURRAY, CA; BROWN, OA; GIBSON, S; WHITE, A; LINTON, EA; PERKINS, AV; LOWENSTEIN, PR; CASTRO, MG

MOLECULAR AND CELLULAR ENDOCRINOLOGY.

ELSEVIER IRELAND LTD

Lugar: Amsterdam; Año: 1998

0303-7207

Procorticotrophin-releasing hormone (proCRH) is expressed mainly in the hypothalamus and in the placenta, where itundergoes tissue-specific endoproteolysis. Our results show that within stably transfected AtT20:D16V cells proCRH is cleaved togenerate two fragments of :8 and 3 kDa which could account for proCRH(125?194) and proCRH(125?151), respectively, anda 4.5 kDa product which could account for mature IR-CRH(1?41). The immunofluorescence staining patterns for IR-CRH andIR-ACTH and their response of secretagogues indicate targeting of proCRH and POMC to the secretory pathway in transfectedAtT20 cells. In this work, we have used a unique set of specific RIAs and IRMAs to the full length POMC and proCRHmolecules and several products of endoproteolytic processing to assess if they could be released differentially in response tostimulation. Although the release of both IR-ACTH and IR-CRH peptides from transfected AtT20 cells is stimulated in responseto exposure to high potassium stimulation (51 mM KCl:5mM CaCl2), the sorting index (SI) suggests that mature ACTH is sortedto the regulated secretory pathway 2.1-fold more efficiently than mature CRH(1?41). Mature ACTH is also sorted to theregulated secretory pathway 9-fold more efficiently than IR-proCRH(125?151). Also, mature CRH(1?41) is sorted to theregulated secretory pathway 3-fold more efficiently than IR-proCRH(125?151). These results therefore indicate that theintracellular mechanisms for the storage and release of POMC, proCRH and their endoproteolytic products differ and wouldsustain the hypothesis that within mammalian peptidergic cells, different biologically active peptides originating from the same ordifferent precursor molecules, could be differentially released in response to specific stimuli. This would give these cells thecapacity to finely regulate neurotransmitter release in response to environmental and physiological demands. © 1998 ElsevierScience Ireland Ltd. All rights reserved.