acylation stimulating protein

Structure

Acylation stimulating protein(ASP) is identical to C3a desArg, which is a cleavage fragment of complement component C3 and has 76 (human, bovine, and porcine) or 77 (mouse and rat) aa residues in mammals. While complement C3 is a glycoprotein, there is no glycosylation site in ASP. ASP has six Cys residues, which make three disulfide bonds

Properties

Mr 8700–9000. pI 7.5–9.5. ASP is soluble in water and a phosphate buffer.

Gene, mRNA, and precursor

The human complement C3 gene, CPAMD1, location 19p13.3, consists of 41 exons. The human C3 mRNA has 5067 b. The human C3 precursor consists of a signal peptide (22 aa residues) and mature C3 (1641 aa residues).

Regulation of synthesis and release

ASP is mainly produced in adipose tissues from the precursor protein complement C3 by posttranscriptional enzymatic cleavage. Ezymatic cleavage of complement C3 by factor B and D (adipsin) forms C3a, and then C3a is rapidly digested by carboxypeptidase B into ASP (C3a desArg). Cytokines such as interleukins 1a, 1b, and 6 and interferon c have been shown to increase C3 production. Hormones such as insulin, glucocorticoids, and estradiol are also involved in augmenting C3 production. Transthyretin, in association with chylomicrons, stimulates C3 and ASP production; this effect is mediated by retinoic acid.

? Clinical implications

ASP is associated with glucose and lipid metabolism in healthy subjects. However, the effect of ASP seems to become dysregulated during metabolic disturbances in diabetes.Chronic ASP administration in mice enhanced the high-fat diet-induced inflammatory response, leading to an insulin-resistant state. The injection of recombinant ASP in diet-induced obesity mice failed to accelerate fat clearance. Furthermore, this ASP injection increased the basal levels of plasma ASP and decreased C5L2 expression in adipose tissues.

Description

Acylation stimulating protein(ASP) is an adipokine that was isolated as a potent fat storage factor. ASP binds to C5L2, which is a functional receptor and promotes triglyceride synthesis in adipose tissues.