Angiopoietin-like proteins are a family of secreted glycoproteins that have strong structural similarity to angiopoietins. They contain a signal peptide, N-terminal coiled-coil domain, and a C-terminal fibrinogen (FBN)-like domain. Angiopoietin-like protein 2 (ANGPTL2) is believed to induce sprouting in endothelial cells through autocrine and paracrine actions. It has been implicated in the metastasis of tumor cells in mouse models. ANGPTL2 is also known as angiopoietin-like 2, angiopoietin-related protein 2 (ARP2), and HARP.
The FBN domain in angiopoietin-like protein 3 (ANGPTL3) interacts with alpha-5 and beta-3 integrins, leading to induction of endothelial cell adhesion and migration. ANGPTL3 may play a role in angiogenesis. It is expressed primarily in the liver and positively correlates with high-density lipoprotein cholesterol (HDL-C) levels. Loss-of-function mutations in one copy of the ANGPTL3 gene are associated with lower levels of low-density lipoprotein cholesterol (LDL-C); in both copies, with lower levels of LDL-C, HDL-C, and triglycerides. ANGPTL3 is also known as angiopoietin-like 3, angiopoietin-5 (ANGPT5), ANG-5, and FHBL2.
Angiopoietin-like protein 4 (ANGPTL4) is directly involved in regulating glucose homeostasis, lipid metabolism, and insulin sensitivity. It also functions as an apoptosis survival factor in vascular endothelial cells. ANGPTL4 is thought to have an antimetastatic function in several cancers; it has been shown to inhibit vascular activity as well as tumor cell motility and invasiveness. Reduced expression of the ANGPTL4 gene has been associated with type 2 diabetes. ANGPTL4 is also known as angiopoietin-like 4, angiopoietin-related protein 4 (ARP4), hepatic fibrinogen/angiopoietin-related protein (HFARP1), peroxisome proliferator-activated receptor (PPAR), PPAR gamma angiopoietin-related protein (PGAR), fasting-induced adipose factor (FIAF), NL2, and pp1158.
ELISAs for Angiopoietin-Like Protein Detection
These kits are solid-phase sandwich ELISAs using two antibodies that are highly specific to human or mouse ANGPTL protein variants; one is precoated on the ELISA plate and the other is HRP-conjugated. These assay kits can be used to measure soluble human or mouse ANGPTL protein variants in serum, EDTA plasma, and cell culture supernatants.