INF1 is a novel microtubule and actin cytoskeleton cross-linking protein

Title: INF1 is a novel microtubule and actin cytoskeleton cross-linking protein
Authors: Thurston, Susan Frances
Date: 2010
Abstract: Formin proteins, characterized by two conserved formin homology (FH) domains, play an important role in cytoskeletal regulation and dynamics. The FH domains are most commonly implicated with the polymerization of F-actin and more recently with the stabilization of microtubules. Inverted formin 1 (INF1) is an atypical formin that has its FH1 and FH2 domains in its N-terminus. The C-terminus of INF1 contains five conserved regions unlike any other sequence found in the database. In this study, we demonstrate that INF1 discreetly associates with microtubules via a unique bipartite microtubule-binding domain (MTBD) in the C-terminus. Additionally, similar to the diaphanous related formin mDia, INF1 induces microtubule stabilization and acetylation. Expression of the MTBD alone, and not the FH2 domain, is sufficient to induce microtubule stabilization. However, in the absence of the MTBD, the N-terminus induces microtubule stabilization dependent on the presence of both the FH1 and the FH2 domains. In addition, knockdown of INF1 protein in NIH 3T3 fibroblasts results in a dramatic loss of acetylated microtubules suggesting INF1 is required for MT acetylation in these cells. Furthermore, we show that INF1 is not regulated by auto-inhibition, but is constitutively active both in vivo and in vitro. Our overexpression results suggest the INF1 C-terminus contains a putative regulatory domain targeted by an unknown inhibitory factor. Finally, we show that INF1 is capable of bundling both microtubules and F-actin simultaneously, implying that INF1 is a cytoskeletal cross-linking protein that could play an important role in cell polarity, cell migration and other cytoskeletal dependent processes.
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
MR61301.PDF4.73 MBAdobe PDFOpen