For years an assumption was made that C-peptide, a
byproduct of insulin biosynthesis, possessed no appreciable
physiologic role. As other contributions in this volume
amply testify, the time has come to re-evaluate that notion.
C-peptide either directly through interaction with its specific
cell-surface receptor or indirectly through an interaction
with a related membrane entity, exerts a unique effect
on several intracellular processes.We review here results of
studies attempting to elucidate such molecular effects of
C-peptide in different cell systems and tissues. Lacking a
purified C-peptide receptor, we also demonstrate C-peptide
effects on distinct elements of the insulin signal transduction
pathways