New Annexin Antibody Panel – Analyzing the Protein Family of Membrane-Managers

The Annexins belong to a group of membrane-binding proteins, who share a conserved C-terminal domain, which contains a Ca2+-dependent phospholipids binding site. They differ by their N-terminal domain, which determines the special function of each annexin.

Annexins are predominantly localized at the cytoplasmic site of the plasma membrane. Although their functions are yet not quite clear defined, it is meanwhile known, that some members of the Annexin family are part of Ca2+-dependent signal transduction pathways as well as exocytotic and endocytotic processes. They also play a role in the regulation of cell growth.

Members of the Annexin-Family

Many members of the Annexin family, like Annexin A1, A3, A4 and A5 show a Phospholipase A2 (PLA2) inhibiting activity. Because PLA2 is necessary for the biosynthesis of potent mediators of inflammation, like prostaglandins and leukotriens, these Annexins have antiinflamatory activity. Annexin A5 inhibits besides PLA2 also the Protein Kinase C (PKC).

Annexin A2 functions as autocrine factor, promoting osteoclast formation and bone resorption.
Some Annexins like Annexin A3 and A4 play a role in the regulation of coagulation an show anticoagulating activity. Annexin A4 also interacts with ATP. It is expressed exclusively in epithelial cells.

Some Annexins like Annexin A5 and A7 are able to work as calcium channels.

Other Annexins, like Annexin A6 (wich has high homology to Annexin A1 and A2) and Annexin A7 have membrane fusing functions, as are required for vesicle fusion during exocytosis, f.e.

Annexin A9 contains 4 Annexin repeats and possibly functions as a low affinity receptor for acetylcholin. It is expressed in stratified, squamous skin epithelium.

Annexins are also implicated in some diseases. Sera of patients having different autoimmune diseases f.e., recognize Annexin A11 as antigen.

The functions of Annexin A13 have not been determined, but it is known to be associated with the plasma membrane of undifferenciated, proliferating endothelial cells and differenciated enterocytes of intestinal villi.

Tab. 1: Human Annexins

Antibodies and Proteins

For studying the function of Annexin, an antibody panel can be a useful tool. We have assorted a vast selection of antibodies and proteins (see table below).

Nearly all listed antibodies are suitable for detection of human annexin in Western blotting. Some Annexin antibodies have already been evaluated for us on formalin-fixed, paraffin embedded sections. The pictures below give samples of such results.

Also included in our Annexin antibody panel ar antibodies that crossreact with other species, like mouse, rat, cattle or pig.

Fig.1: Annexin A4 Staining Immunohistochemical staining of paraffin sections from human intestine using Annexin A4 antibody ARP36686. Arrows indicate Annexin A4 positive epithial cells of intestinal villus.

Fig.2: Annexin A3 Staining Immunohistochemical staining of paraffin sections from human spleen using Annexin A3 antibody ARP36578. Arrows indicate Annexin A3 positive cells.

Fig.3: Annexin A1 Staining Immunohistochemical staining of paraffin sections from human intestine using Annexin A1 antibody ARP36568. Arrows indicate Annexin A1 positive epithelial cells.

Reference:

Gerke, V and Moss, SE (2002) Annexins: From Structure to Function. Physiol. Rev. 82 (2): 331-71

Monastyrskaya K, Babiychuk EB, Hostettler A, Rescher U, Draeger A. Annexins as intracellular calcium sensors. Cell Calcium. 2007 Mar;41(3):207-19.

Skrahina T, Piljic A, Schultz C. Heterogeneity and timing of translocation and membrane-mediated assembly of different annexins. Exp Cell Res. 2008 Mar 10;314(5):1039-47.

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