Protein prevents excess fluid from entering lung tissue

A protein found in the cells lining blood vessels plays a central role in preventing fluid and inflammatory cells from leaking into lung tissue in a low-oxygen environment.

Annexin A2 is one of the proteins found in the junctions between tightly packed endothelial cells, which line blood vessels. The junctions function like gates keeping fluid out. When oxygen is low in the lung, compounds called phosphates can stick onto the gates, jamming them open and allowing fluid and inflammatory cells to pass into tissue. Annexin A2 links with another protein called vascular endothelial cadherin (VEC) and two enzymes, endothelial-specific protein tyrosine phosphatase and Src homology phosphatase-2, that help remove the phosphates and keep the gates closed.