Identification by immunoblotting of somatostatin proforms in a rat pancreatic cell line.
The immunoblotting technique is applied to the analysis of "somatostatin" compounds secreted by R.I.N. T3 cells. We can confirm that two proforms of 15,300 +/- 750 and 29,000 +/- 1,100 Da accumulate in the extracellular medium. The unexpected form of 29 kDa, probably a dimeric form, disappears in reducing conditions. However, the 15 kDa peptide is characterized by several antibodies directed against either the intramolecular cycle of somatostatin-14 or the N-terminal extension of somatostatin-28. The 15 kDa form presents the same electrophoretic mobility in SDS-PAGE than the prosomatostatin isolated from a hypothalamic extract. Furthermore, this compound corresponds to the calculated mass of 10,388 Da deduced from the cDNA sequence. The detection of an immunoreactive 6 kDa peptide in the gel filtration fractions suggests an intermediate step in the prosomatostatin processing in these cells.
Lherisson
C
C
INSERM, U151 Toulouse, France.
Svoboda
M
M
Pradayrol
L
L
Estival
A
A
Christophe
J
J
Vaysse
N
N
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002460:Cell Line; D010179:Pancreas / Q000032:analysis*; D011498:Protein Precursors / Q000032:analysis*; D051381:Rats; D013004:Somatostatin / Q000032:analysis*
D011498:Protein Precursors; D013004:Somatostatin; C028456:prosomatostatin