Somatostatin-28 [1-12]-like peptides

Area of Science:

• Neuroendocrinology
• Molecular Biology
• Biochemistry

Background:

• The prosomatostatin system, including somatostatin-14 (SS-14) and somatostatin-28 (SS-28), plays crucial roles in physiological processes.
• The NH2-terminus of SS-28 and its related peptides have been less characterized compared to SS-14 and SS-28.

Purpose of the Study:

• To isolate and characterize peptides corresponding to the NH2-terminus of somatostatin-28 (SS-28) in mammalian tissues.
• To investigate the distribution and potential origins of these novel somatostatin-related peptides.

Main Methods:

• Peptide isolation from pancreas and hypothalamus using chromatographic techniques (ion-exchange, gel permeation, reverse-phase HPLC).
• Immunohistochemistry to determine the distribution of somatostatin-28[1-12]-like immunoreactivity (SS-28[1-12]-LI) in rat brain.
• Amino acid analysis and partial sequencing of isolated peptides, compared with rat pre-prosomatostatin (prepro-SS) cDNA sequence.

Main Results:

• Somatostatin-28[1-12] (SS-28[1-12]) was isolated and found to be widely distributed in the central nervous and digestive systems.
• Two precursor peptides, 8K (prepro-SS[25-100]) and 5K (prepro-SS[57-100]), were identified in rat tissues, with 8K being released from hypothalamic tissue.
• SS-28[1-12]-LI was concentrated in specific nerve fibers and terminals within the rat brain, including the median eminence and neocortex.

Conclusions:

• The prosomatostatin system involves multiple peptides, including SS-28[1-12] and its precursors, with distinct tissue distributions.
• Prepro-SS can serve as a direct precursor for SS-14, bypassing SS-28, and other peptides may derive from cryptic regions of the precursor.
• The 8K peptide (prepro-SS[25-100]) is secreted, suggesting a role in intercellular communication, while the 5K peptide is not.