Interactions of vitronectin and plasminogen with Helicobacter pylori

Sammanfattning: Helicobacter pylori is the main cause of chronic gastritis and peptic ulcer disease in man and is also associated gastric cancer. The spiral shaped H. pylori moves through the gastric mucous layer and colonises the gastric epithelial cells. H. pylori adheres to specific mucosal structures, including mucus molecules, epithelial cells, glycoconjugates and extracellular matrix (ECM) proteins. The ECM is exposed after disruption of the gastric epithelium through the action of the vacuolating toxin A and other mechanisms. The binding of two ECM-proteins, vitronectin and plasminogen to H. pylori was investigated. It was observed that vitronectin binding to H. pylori varies among strains, in a sialic acid dependent manner and correlates to their haemagglutinating ability. The binding was pH dependent, protease and heat sensitive, suggesting that cell surface proteins bind vitronectin. Furthermore, a vitronectin binding protein (57 kDa and a pI of 8.7) of H. pylori CCUG 17874, was identified by two dimensional electrophoresis and Western blot. The amino-terminal amino acid sequence of the vitronectin binding protein was shown to be identical with the NH2-terminal of H. pylori catalase. The binding of plasminogen to H. pylori was a common phenomenon among H. pylori strains, and independent of the morphological state, spiral or coccoid. H. pylori CCUG 17874 interacts with plasminogen at the fifth kringle of the plasminogen molecule, through two cell surface proteins (42 and 57 kDa), distinct from the vitronectin binding protein. H. pylori surface bound plasminogen can be activated to plasmin, in the presence of tissue type plasminogen activator (tPA). The formation of H. pylori surface bound plasmin may be a mechanism to degrade ECM, and could prolong the healing process of gastric ulcers.