Flemming Cornelius

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Se relationer på Aarhus Universitet

Flemming Cornelius - P-type ATPases

Our research has been concerned with the structure, function and regulation of P-type ATPases, mainly Na,K-ATPase and H,K-ATPase. We are using preparations from pig kidney (NKA), pig stomach (HKA), and shark salt glands (NKA). The latter has been used as a model tissue for Cl- secreting epithelia in all vertebrates from sharks to mammals.

The steady state and pre-steady state kinetics and electrogenic properties of the overall and partial reactions of Na,K-ATPase have been investigated over the last three decades using biochemical and biophysical methods including stopped-flow fluorescence and quenched-flow measurements. Within the last decade our main line of research has shifted to a more cell biological approach.

Since our discovery and characterization of a new regulatory protein (PLMS, phospholemman-like protein from shark) specifically associated with Na,K-ATPase from the salt gland of the shark [1] it has become clear that the activity of Na,K-ATPase in various species and tissues is finely regulated by interaction with a group of small, single-spanning proteins called the FXYD proteins [2]. Besides the one in shark (now termed FXYD10) 7 mammalian species are known, which are differentially expressed in various tissues. Thus, in the kidney mainly FXYD2 and FXYD4 are expressed, whereas in myocardium and skeletal muscle FXYD1 is expressed, and FXYD7 is expressed specifically in the brain.

Some FXYD proteins exert their effects on the Na,K-ATPase depending on their state of phosphorylation as regulated by protein kinases/phosphatases. This regards e.g. FXYD1, FXYD7 and FXYD10. We have characterized this protein kinase dependent interaction of FXYD10 with the Na,K-ATPase in a series of papers e.g. using molecular cross-linking as a tool [3- ].

Another line of research has been investigation of the interactions of phospholipids and cholesterol with the Na,K-ATPase. For this we use reconstitution of Na,K-ATPase into small lipid vesicles (liposomes) of defined lipid composition [ ]. Indeed, cholesterol seems to play a crucial role in supporting Na,K-ATPase activity [ - ], a fact that has led to the suggestion of specific interaction (binding) of cholesterol with Na,K-ATPase.

Recently we have been engaged in research concerning the molecular 3D structure of Na,K-ATPase  using x-ray crystallography. By this we hope to gain more specific insight into the structure and interactions of the three subunits of Na,K-ATPase: the catalytic alpha-subunit, the beta-subunit and the FXYD protein. This research is performed in collaboration with C. Toyoshima's group in Tokyo, Japan.

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