Secretagogin is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''SCGN''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

Expression

Secretagogin is expressed in a variety of organs and tissues. It is expressed in pancreatic β cells, where it participates in insulin release. In the brain, it is expressed in interneurons and pyramidal cells of the hippocampus. In the brainstem, it is expressed neurons of the superior colliculus, cuneiform nucleus, locus coeruleus, and solitary tract nucleus. In the spinal cord, secretagogin is expressed in the dorsal horn and dorsal root ganglia (up to 7% of DRGs) where it is co-expressed with calcitonin gene-related peptide (CGRP). Secretagogin is also expressed in the sciatic nerve. In gut tissue, secretagogin is expressed in 10% of enteric neurons of the small intestine, while it is expressed in 5% of enteric neurons of the proximal colon, and 25% in the distal colon. Single-cell RNA sequencing of human and mouse intestinal tissue suggests that secretagogin is also expressed in about 15% of enteroendocrine cells. There are notable differences in secretagogin expression between mice and humans, particularly in the brain. For example, secretagogin is most highly expressed in the cerebellum of humans, while in mice the olfactory bulb has the most secretagogin-expressing neurons.

Function

The encoded protein is a secreted

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

-binding protein which is found in the

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

. It is related to calbindin D-28K and

calretinin Calretinin, also known as calbindin 2 (formerly 29 kDa calbindin), is a calcium-binding protein involved in calcium signaling. In humans, the calretinin protein is encoded by the ''CALB2'' gene. Function This gene encodes an intracellular ...

. This protein is thought to be involved in

potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a sa ...

-stimulated calcium flux and

cell proliferation Cell proliferation is the process by which ''a cell grows and divides to produce two daughter cells''. Cell proliferation leads to an exponential increase in cell number and is therefore a rapid mechanism of tissue growth. Cell proliferation ...

. This protein plays an important role in the release of the stress hormone

Corticotropin-releasing hormone Corticotropin-releasing hormone (CRH) (also known as corticotropin-releasing factor (CRF) or corticoliberin; corticotropin may also be spelled corticotrophin) is a peptide hormone involved in stress responses. It is a releasing hormone that b ...

(CRH) and which only then enables stress processes in the brain. Within pancreatic β cells, secretagogin assists in insulin release, particularly in scaling insulin release to glucose levels. It does this by interacting with the actin cytoskeleton and synaptic release machinery such as SNAP-25. Deletion of secretagogin disrupts the membrane-specific localization of SNAP-25, suggesting that secretagogin is critical for the assembly of synaptic release machinery. In human fetal brain development, secretagogin is expressed in neocortical GABAergic neurons that migrate from the central and lateral ganglionic eminences. Secretagogin expression in these populations is highest right before birth, and wanes into adulthood. When secretagogin was overexpressed in embryonic neurons, their total neurite length and the number of branches increased, suggesting that secretagogin may play a role in neuronal arborization.

Expression

Function

References

Further reading