ABSTRACT
The actin filament-associated protein of 110 kDa (AFAP-110) is a Src binding partner that represents a potential modulator of actin filament integrity in response to cellular signals. Previous reports have demonstrated that AFAP-110 is capable of directly binding and altering actin filaments. Deletion of the leucine zipper motif of AFAP-110 (AFAP-110(Deltalzip)) has been shown to induce a phenotype which resembles Src-transformed cells, by repositioning actin filaments into rosettes. This deletion also mimics a conformational change in AFAP-110 that is detected in Src-transformed cells. The results presented here indicate that unlike AFAP-110, AFAP-110(Deltalzip) is capable of activating cellular tyrosine kinases, including Src family members, and that AFAP-110(Deltalzip) itself is hyperphosphorylated. The newly tyrosine phosphorylated proteins and activated Src-family members appear to be associated with actin-rich lamellipodia. A point mutation that alters the SH3-binding motif of AFAP-110(Deltalzip) prevents it from activating tyrosine kinases and altering actin filament integrity. In addition, a deletion within a pleckstrin homology (PH) domain of AFAP-110(Deltalzip) will also revert its effects upon actin filaments. Lastly, dominant-positive RhoA(V14) will block the ability of AFAP-110(Deltalzip) from inducing actin filament rosettes, but does not inhibit Src activation. Thus, conformational changes in AFAP-110 enable it to activate cellular kinases in a mechanism requiring SH3 and/or PH domain interactions. We hypothesize that cellular signals which alter AFAP-110 conformation, enable it to activate cellular kinases such as cSrc, which then direct changes in actin filament integrity in a Rho-dependent fashion.
Subject(s)
Actin Cytoskeleton/ultrastructure , Microfilament Proteins/physiology , Phosphoproteins/physiology , src-Family Kinases/metabolism , Animals , COS Cells , Cytoplasm/metabolism , Cytoskeleton/ultrastructure , Enzyme Activation , Leucine Zippers , Microfilament Proteins/chemistry , Microfilament Proteins/genetics , Microscopy, Fluorescence , Models, Biological , Mutation , Phosphoproteins/chemistry , Phosphoproteins/genetics , Phosphorylation , Phosphotyrosine/metabolism , Transfection , rhoA GTP-Binding Protein/physiology , src Homology DomainsABSTRACT
A marked prophylactic effect of dibasole and ascorbic acid in influenza and other acute respiratory diseases (ARD) is described. The analysis was based on comparison with a control group observed for the same period and being at the same risk of contracting infection with influenza or other ARD. The control group was given glucose according to the same procedure.
