ABSTRACT
Recent evidence has suggested that activation of phosphoinositide 3-kinase (PI 3-kinase) is required for the activation of Akt-1 by growth factors and insulin. Here we demonstrate by two independent methods that Akt-1 from L6 myotubes binds to PtdIns(3,4,5)P3, PtdIns(3,4)P2 and PtdIns(4,5)P2 when presented against a background of phosphatidylserine (PtdSer) or a 1:1 mixture of PtdSer and phosphatidylcholine (PtdCho). No binding was observed with the lipids PtdIns(3,5)P2, PtdIns4P and PtdIns3P or background lipids. Activated, hyperphosphorylated forms of Akt-1 from insulin-stimulated L6 myotubes bound to PtdIns(3,4,5)P3 in a similar manner as inactive Akt-1. Quantitative analysis using surface plasmon resonance showed that the equilibrium association constant for the binding of Akt-1 to PtdIns(3,4,5)P3 was submicromolar and that PtdIns(3,4)P2 and PtdIns(4,5)P2 bound to Akt-1 with 3- and 6-fold lower affinities respectively. Interaction of Akt-1 with PtdIns(3,4,5)P3 did not activate the protein kinase activity, either before or after incubation with MgATP. A model is presented in which PtdIns(3,4,5)P3 may prime Akt-1 for activation by another protein kinase, perhaps by recruiting it to the plasma membrane.
Subject(s)
Phosphatidylinositol Phosphates/metabolism , Protein Serine-Threonine Kinases , Proto-Oncogene Proteins/metabolism , Amino Acid Sequence , Animals , Cell Line , Enzyme Activation/drug effects , Kinetics , Liposomes , Models, Biological , Molecular Sequence Data , Peptide Fragments/genetics , Peptide Fragments/immunology , Phosphatidylinositol Phosphates/pharmacology , Protein Binding , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins/immunology , Proto-Oncogene Proteins c-akt , RatsABSTRACT
As professional service providers continue to face an increasingly competitive environment, marketing becomes a more attractive prospect. One marketing activity that has emerged in recent years is the retailing of products related to one's profession directly from the office. The authors explore the retailing phenomenon from the perspective of dentists and dental patients and find that patients are less critical of the practice than dentists are themselves.
Subject(s)
Dental Health Services/economics , Marketing of Health Services , Data Collection , Dental Health Services/standards , Health Services Research , Patient Satisfaction/statistics & numerical data , United StatesABSTRACT
Providers of professional services are beginning to experiment with promotional activities as a means to increase business and to remain competitive in the 1990s. The authors report the results of a nationwide survey of dentists that was conducted to identify the incidence and impact of promotional tool use among dental professionals. Of particular interest is the effect of different promotional tools on dentists' patient contact activity. Interestingly, dentists employed a variety of promotional tools in their practices and generally viewed promotion as acceptable. Yet, only dentists who used publicity as their sole promotional mechanism reported significantly improved patient contact activity.
