Annexin

Annexin is a common name for a group of cellular proteins. They are mostly found in eukaryotic organisms (animal, plant and fungi).

In humans, the annexins are found inside the cell. However some annexins (Annexin A1, Annexin A2, and Annexin A5) have also been found outside the cellular environment, for example, in blood. How the annexins are transported out of the cell into the blood is a mystery because they lack a signal peptide necessary for proteins to be transported out of the cell.

Annexin is also known as lipocortin. Lipocortins suppress phospholipase A2. Increased expression of the gene coding for annexin-1 is one of the mechanisms by which glucocorticoids (such as cortisol) inhibit inflammation.

Introduction

The protein family of annexins has continued to grow since their association with intracellular membranes was first reported in 1977. The recognition that these proteins were members of a broad family first came from protein sequence comparisons and their cross-reactivity with antibodies. One of these workers (Geisow) coined the name Annexin shortly after.

Annexin A2

Annexin A2 also known as annexin II is a protein that in humans is encoded by the ANXA2 gene.

Annexin 2 is involved in diverse cellular processes such as cell motility (especially that of the epithelial cells), linkage of membrane-associated protein complexes to the actin cytoskeleton, endocytosis, fibrinolysis, ion channel formation, and cell matrix interactions. It is a calcium-dependent phospholipid-binding protein whose function is to help organize exocytosis of intracellular proteins to the extracellular domain. Annexin II is a pleiotropic protein meaning that its function is dependent on place and time in the body.

Gene

The ANXA2 gene, located at 15q22.2, has three pseudogenes located on chromosomes 4, 9 and 10, respectively. Multiple alternatively spliced transcript variants encoding different isoforms have been found for this gene.

Function

This protein is a member of the annexin family. Members of this calcium-dependent phospholipid-binding protein family play a role in the regulation of cellular growth and in signal transduction pathways. This protein functions as an autocrine factor which heightens osteoclast formation and bone resorption.