Date of Award
Doctor of Philosophy (PhD)
Dr. Richard Epand
It has been shown previously that the biophysical properties of the membrane influence the ability of protein kinase C (PKC) to bind to it and become activated. The mechanism by which this occurs has not been firmly established. The following studies were undertaken to elucidate the roles of membrane structure in modulating PKC. This was accomplished by determining the effects that a defined change in membrane structure had on the binding and catalysis of PKC, by addition of phospholipids or other compounds to lamellar phase membranes, or through the use of non-lamellar phases. Also, the role of hydration in binding and catalysis was studied. Unsaturated phosphatidylethanolamines (PEs) were found to be activators of the enzyme, when added to large unilamellar vesicles (LUVs). Relative activation caused by different PEs correlated with their bilayer to hexagonal phase transition temperatures (TH S), but the extent of activation was not always proportional to the effect on TH since two PEs which caused similar levels of activation did not cause a similar change in TH . Activation was found to correlate best with the interfacial polarity of LUVs containing the PEs. Other properties of the phospholipid, such as its intrinsic radius of curvature, and its bending modulus, as well as the actual curvature strain it imposes on the LUVs did not correlate with the activation seen. Cubic phases were found to activate membrane-bound PKC to a greater extent than LUVs of similar composition which possessed a higher level of curvature strain. Hexagonal phases, containing the lowest level of curvature strain, supported levels of activation similar to that of lamellar phases. Lipophosphoglycan from Leishmania donovani , was a potent inhibitor of membrane-bound PKC, which could exert its effects from the opposite monolayer of the bilayer to which the enzyme binds. Polyethylene-glycol linked PEs were also found to inhibit the membrane-bound form of the enzyme.
Giorgione, Jennifer, "The modulation of protein kinase C by hydration and membrane spontaneous curvature" (1999). Open Access Dissertations and Theses. Paper 1844.