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.