Biosynthesis and processing of delta sleep‐inducing peptide‐like precursors in primary cultures of mouse anterior pituitary cells

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Abstract
The biosynthesis and processing of material resembling delta sleep‐inducing peptide (DSIP) have been studied in mouse anterior pituitary primary cell cultures. Cells were pulse/chase incubated with 3H‐labelled amino acids (Gly, Arg or Ala) and cell extracts were immunoprecipitated with DSIP antiserum. Labelled DSIP‐related proteins were resolved by SDS/PAGE. Multiple forms of DSIP‐immunoprecipitable material were observed, including three precursors of molecular mass 50–60 kDa which were processed to two major groups of intermediates of 35–45 kDa and 9–16.5 kDa. These intermediates appear to be processed to a DSIP‐related peptide (molecular mass < 3 kDa), which co‐ran on reversed‐phase HPLC with an endogenous form of DSIP in mouse anterior pituitary, but not with rabbit DSIP. This < 3‐kDa peptide incorporated [3H]Gly, but not [3H]Arg or [3H]Ala. In addition, it incorporated [3H]glucosamine, indicating that it was a glycopeptide. Secretion studies showed release of the < 3‐kDa DSIP‐like glycopeptide and the 9–16.5‐kDa group of intermediates into the medium. The present study demonstrates the biosynthesis of a small DSIP‐like glycopeptide in mouse anterior pituitary cells, which is not identical with, but has similarities to, rabbit DSIP.