Authors: Gallois D.¹; Brisorgueil M-J.²; Conrath M.²; Mailly P.²; Soyez D.¹

Source: European Journal of Cell Biology, Volume 82, Number 8, August 2003 , pp. 431-440(10)

Publisher: Urban & Fischer

Abstract:

Isomerization of the third amino acid residue (a phenylalanine) of crustacean hyperglycemic hormone (CHH) has been previously reported to occur as a late step of hormone precursor maturation in a few neurosecretory cells in the X-organ-sinus gland complex of the crayfish Orconectes limosus. In the present report, using conformation-specific antisera combined with immunogold labeling, we have studied, at the ultrastructural level, the distribution of L- and D-CHH immunoreactivity in CHH-secreting cells of the crayfish Astacus leptodactylus. Two CHH-secreting cell populations were observed, the first one (L-cells), the most numerous, exhibited only labeling for L-CHH. In the second one (D-cells), four secretory granule populations were distinguished according to their labeling: unlabeled, either L- or D- exclusively or both L- and D-granules. Labeling quantification by image analysis in D-cells showed a marked increase in D-labeling from the cell body to the axon terminal. However some L- and mixed granules remain in axon terminals. Our results demonstrate that Phe³ isomerization of CHH occurs within the secretory granules of specialized neurosecretory cells and progresses as the granules migrate along the axonal tract. The observation that not all the CHH synthesized is isomerized, and the great variability in the proportion of L- and D-immunoreactivity in granules in every cell region may suggest an heterogeneous distribution of the putative enzyme involved in Phe³ isomerization, a peptide isomerase, within the secretory pathway.

Document Type: Research article

DOI: http://dx.doi.org/10.1078/0171-9335-00329

Affiliations: 1: Groupe Biogenèse des Peptides Isomères, UMR CNRS 7079 Physiologie et Physiopathologie, Université Pierre et Marie Curie, Paris/France 2: UMR CNRS 7101, Neurobiologie des Signaux Intercellulaires, Université Pierre et Marie Curie, Paris/France

Publication date: 2003-08-01

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