Cortistatin: Molecular Structure

Molecular Structure and Properties#

Cortistatin-14 (CST-14) is a 14-amino-acid cyclic neuropeptide with a molecular weight of 1,721.01 Da, molecular formula C81H113N19O19S2, and CAS number 193829-96-8. It was first isolated from rat cerebral cortex in 1996 and subsequently identified in humans. The peptide is derived from a 112-amino-acid precursor (preprocortistatin) encoded by the CORT gene.

Amino Acid Sequence#

Cortistatin-14 (Human)#

The primary sequence of human cortistatin-14 is:

P-C-K-N-F-F-W-K-T-F-S-S-C-K

An intramolecular disulfide bond between Cys2 and Cys13 creates the cyclic structure essential for biological activity. This cyclic motif is conserved across species and shared with somatostatin-14.

Comparison with Somatostatin-14#

Cortistatin-14 shares 11 of 14 positions with somatostatin-14 when optimally aligned, with the core FWKTFSS/TC motif being highly conserved. Despite this homology, cortistatin and somatostatin are products of separate genes located on different chromosomes.

Cortistatin-17#

A longer form, cortistatin-17 (CST-17), includes a 3-residue N-terminal extension (Asp-Arg-Met-) prepended to the cortistatin-14 sequence. CST-17 retains biological activity and represents an alternative processing product of preprocortistatin.

Disulfide Bond and Cyclic Structure#

The Cys2-Cys13 disulfide bond constrains cortistatin-14 into a cyclic conformation that is critical for receptor binding. This cyclic motif is shared with somatostatin-14 (which has a Cys3-Cys14 disulfide) and is required for binding to somatostatin receptors. Reduction of the disulfide bond abolishes receptor binding and biological activity.

Receptor Binding Profile#

Cortistatin binds a broader range of receptors than somatostatin:

• sst1: High affinity (comparable to somatostatin)
• sst2: High affinity (comparable to somatostatin)
• sst3: High affinity (comparable to somatostatin)
• sst4: High affinity (comparable to somatostatin)
• sst5: High affinity (comparable to somatostatin)
• GHSR-1a (ghrelin receptor): Moderate affinity (unique to cortistatin; somatostatin does not bind)
• MrgX2: Activates this Mas-related GPCR (unique to cortistatin)

The ability to bind the ghrelin receptor distinguishes cortistatin from somatostatin and may explain cortistatin's distinct effects on growth hormone release, feeding behavior, and immune function.

Physicochemical Properties#

• Solubility: Soluble in aqueous buffers at physiological pH; the cyclic structure provides moderate stability
• Stability: More stable than linear peptides due to the disulfide constraint, but still susceptible to proteolytic degradation in vivo
• Half-life: Short (estimated minutes in vivo), consistent with other neuropeptides; this limits therapeutic application without structural modification

Gene and Expression#

The CORT gene encodes preprocortistatin and is located on chromosome 1 in humans. Expression is highly restricted to the central nervous system, particularly:

• Cerebral cortex: Subset of GABAergic interneurons (partially overlapping with somatostatin-positive interneurons)
• Hippocampus: CA1 and CA3 pyramidal layer interneurons
• Peripheral immune cells: Low-level expression detected in macrophages, dendritic cells, and T cells

Expression is regulated by neuronal activity, with BDNF serving as a key upstream regulator. Preprocortistatin mRNA follows a circadian pattern and is upregulated by sleep deprivation.

Related Reading#

• Cortistatin overview and research guide
• Peptides similar to Cortistatin
• Cortistatin research evidence