Localization of alpha-endosulphine in pancreatic somatostatin delta cells and expression during rat pancreas development.
OBJECTIVE
alpha-Endosulphine, a protein that belongs to the cAMP-regulated-phosphoprotein family, has been reported to modulate insulin secretion in vitro through interaction with the pancreatic beta-cell ATP-sensitive potassium (K(ATP)) channel. In this study, we analysed the tissue distribution of alpha-endosulphine and determined its pancreatic cellular localization.


METHODS
Quantitative tissue distribution of alpha-endosulphine was studied by RIA on tissue extracts and cellular/subcellular localization was done using immunocytochemistry, morphometry and western blot analysis. alpha-Endosulphine and somatostatin release from RINT-3 somatostatin-secreting cells was quantified by RIA.


RESULTS
alpha-Endosulphine, concentrated particularly in the central nervous system, was also detected in a wide variety of tissues including the pancreas. Immunohistochemistry analysis of adult rat pancreatic sections showed that alpha-endosulphine localized in somatostatin delta cells, where its expression increased during post-natal development. Immunoreactive cells were detected from foetal age E19, and the number of somatostatin cells co-expressing alpha-endosulphine increased with developmental age from E19 until adult. alpha-Endosulphine, highly expressed in the cytoplasm of RINT3 somatostatin-secreting cell line, was recovered in the particulate fraction of RINT3 cell extracts but was not co-secreted with somatostatin.


CONCLUSIONS
alpha-Endosulphine is expressed in all tissues tested including pancreas and is also detected in plasma. Pancreatic alpha-endosulphine is specifically localized in somatostatin delta cells. This cytosolic protein is not co-secreted with somatostatin and could be physically associated with particulate components of the cells. These findings are not in favour of an endocrine/paracrine effect of alpha-endosulphine on the beta-cell K(ATP) channel.
Gros
L
L
INSERM U376, CHU Arnaud-de-Villeneuve, Montpellier, France. lgros@u376montp.inserm.fr
Bréant
B
B
Duchene
B
B
Leroy
C
C
Fauconnier
G
G
Bataille
D
D
Virsolvy
A
A
D000375:Aging; D000818:Animals; D002460:Cell Line; D029721:Drosophila Proteins; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D036341:Intercellular Signaling Peptides and Proteins; D007515:Islets of Langerhans / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism; D007700:Kinetics; D010179:Pancreas / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin
D029721:Drosophila Proteins; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C483180:endos protein, Drosophila; C075663:endosulfine; D013004:Somatostatin