Insulin prohormone processing, distribution, and relation to metabolism inAplysia californica

The first Aplysia californica insulin gene is characterized and its proteol ytic processing from prohormone to final peptides elucidated using a combin ation of biochemical and mass spectrometric methods. Aplysia insulin (AI) i s one of the largest insulins found, with a molecular weight of 9146 Da, an d an extended A chain compared with other invertebrate and vertebrate insul ins. The AI prohormone produces a series of C peptides and also a unique N- terminally acetylated D peptide. Al-producing cells are restricted to the c entral region of the cerebral ganglia mostly within the F and C clusters, a nd AI is transported to neurohemal release sites located on the upper labia l and anterior tentacular nerves. The expression of AI mRNA decreases when the animal is deprived of food, and injections of AI reduce hemolymph gluco se levels, suggesting that the function of insulin-regulating metabolism ha s been conserved.