title: Effect of Cdc42 domains on filopodia sensing, cell orientation, and haptotaxis.
abstract: Filopodia are sensors which, along with microtubules, regulate the persistence of locomotion. To determine whether protrusions were involved in sensing adhesion, epithelial cells were cultured on platinum and tantalum gradients. Protrusions were defined by an unbiased statistical method of classification as factors 4 (filopodia), 5 (mass distribution), and 7 (nascent neurites). When the prevalence of protrusions was measured in zones of high (H), middle (M), and low (L) adhesiveness, the main differences were in factor 4. Its values were highest at H and declined at M and L regardless of the gradient composition. The significance of the differences was enhanced when T (top/adhesive end) and B (bottom/nonadhesive end) sides of cells were analyzed separately. Since information about sidedness increased the statistical power of the test, this result suggested that cells pointed more filopodia toward the adhesive end. Trends occurred in factors 5 and 7 only when conditions allowed for a marked trend in factor 4. The data showed that gradient sensing is proportional to the prevalence of filopodia, and filopodia are the only protrusions engaged in comparing adhesiveness across a cell. The probability (P) of the significance of a trend was then used to determine how cells sense the gradient. Binding peptides (BPs) were introduced representing sequences critical for Cdc42 docking on a specific partner. BPs for IQGAP (IQ(calmodulin-binding domain)-containing GTPase-activating protein) and ACK (Cdc42-associated kinase) reduced factor 4 values and prevented cell orientation on the gradient. Micrographs showed attenuated or stubby filopodia. These effectors may be implicated in gradient sensing. Another IQGAP BP increased filopodia prevalence and enhanced orientation on the gradient (P<0.00015). A Wiskott-Aldrich syndrome protein (WASP) BP had no effect. When sensing and orientation were abolished, they both failed at the level of filopodia, indicating that filopodia are both sensors and implementers of signals transduced by adhesion.
authors.affiliation: Center for Microscopy and Microanalysis, Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, United States.
authors.forename: Surya P
authors.initials: SP
authors.lastname: Amarachintha
authors.affiliation: Department of Applied Statistics and Operations Research, Bowling Green State University, Bowling Green, OH 43403, United States.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Ryan
authors.affiliation: Center for Microscopy and Microanalysis, Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, United States.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Cayer
authors.affiliation: Department of Applied Statistics and Operations Research, Bowling Green State University, Bowling Green, OH 43403, United States.
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Boudreau
authors.affiliation: Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, United States.
authors.forename: Nathan M
authors.initials: NM
authors.lastname: Johnson
authors.affiliation: Center for Microscopy and Microanalysis, Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, United States; Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, United States.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Heckman
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002460:Cell Line; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D051744:Protein Kinase C-epsilon / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011554:Pseudopodia / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013635:Tantalum / Q000494:pharmacology; D051316:Wiskott-Aldrich Syndrome Protein / Q000037:antagonists & inhibitors / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020703:ras GTPase-Activating Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C101203:IQ motif containing GTPase activating protein 1; C504908:Pard6a protein, rat; D051316:Wiskott-Aldrich Syndrome Protein; D020703:ras GTPase-Activating Proteins; D013635:Tantalum; D011505:Protein-Tyrosine Kinases; C509145:Tnk2 protein, rat; D051744:Protein Kinase C-epsilon; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein
keywords: Adhesion; Blocking peptide; Latent factor analysis; Mechanotransduction; Nerve guidance; Persistence