Coordination of microtubules and the actin cytoskeleton by the Rho effector mDia1

Abstract

Coordination of microtubules and the actin cytoskeleton is important in several types of cell movement. mDia1 is a member of the formin-homology family of proteins and an effector of the small GTPase Rho. It contains the Rho-binding domain in its amino terminus and two distinct regions of formin homology, FH1 in the middle and FH2 in the carboxy terminus. Here we show that expression of mDia1(DeltaN3), an active mDia1 mutant containing the FH1 and FH2 regions without the Rho-binding domain, induces bipolar elongation of HeLa cells and aligns microtubules in parallel to F-actin bundles along the long axis of the cell. The cell elongation and microtubule alignment caused by this mutant is abolished by co-expression of an FH2-region fragment, and expression of mDia1(DeltaN3) containing point mutations in the FH2 region causes an increase in the amount of disorganized F-actin without cell elongation and microtubule alignment. These results indicate that mDia1 may coordinate microtubules and F-actin through its FH2 and FH1 regions, respectively.

The RhoA Effector mDia Is Induced During T Cell Activation and Regulates Actin Polymerization and Cell Migration in T Lymphocytes

“…Previous studies in HeLa cells demonstrated that exogenously introduced mDia localized to the perinuclear zone and to podosome-like regions in the periphery of the cell (28). Our data show that both endogenous and overexpressed mDia localize to the leading edge, but only scarcely at the leading lamella.…”

“…The activated mutant of p160ROCK (⌬4-ROCK) and the kinase-dead mutant (KD-ROCK) have been previously described (33). The wild-type enhanced green fluorescence protein (EGFP)-mDia, activated mutant EGFP-mDia ⌬N3, EGFP-mDia F2, and EGFP-mDia ⌬N3 (HindIII) have been described previously (18,28). EGFP-mDia F1 (aa 570 -735) was generated by PCR (primers 5Ј-GGAA GATCTGCTGCTGTTCCCCTG-3Ј and 3Ј-AGGGGGCCCAAATCCAAA GGGGGGAGGT-5Ј), cloned in-frame in BglII/SmaI of the multiple cloning site of pEGFP-C1, and confirmed by sequencing.…”

Role of Rho family GTPases in epithelial morphogenesis

“…In this system, Rok activates the actin-based molecular motor myosin II to exert tension force on actin filaments during stress fiber formation, whereas Dia1 seems to contribute to the determination of nucleation sites for actin filaments. More recent studies in fibroblasts and HeLa cells demonstrate a role for Dia1 as mediator of RhoA's effects on microtubule stabilization in the leading edge (Ishizaki et al 2001;Palazzo et al 2001a). Based on these observations, it has been speculated that Dia1 could play a role in regulating the assembly or maintenance of the hair cell cytoskeleton (Müller and Littlewood-Evans 2001).…”

PKD2 Interacts and Co-localizes with mDia1 to Mitotic Spindles of Dividing Cells

“…The FH1 domain binds profilin, an actin-binding protein (20), and Src homology 3 domains containing proteins such as Src (28) and IRSp53/BAIAP2 (29). The FH2 domain has been reported to be involved in coordinating microtubules and the actin cytoskeleton during cell movement (30). mDia1 contains a 173-amino acid region in the C terminus of its FH3 domain that is necessary for mDia1 localization to mitotic spindles in HeLa cells (31).…”