Enlazin, a Natural Fusion of Two Classes of Canonical Cytoskeletal Proteins, Contributes to Cytokinesis Dynamics

Abstract

Cytokinesis requires a complex network of equatorial and global proteins to regulate cell shape changes. Here, using interaction genetics, we report the first characterization of a novel protein, enlazin. Enlazin is a natural fusion of two canonical classes of actin-associated proteins, the ezrin-radixin-moesin family and fimbrin, and it is localized to actin-rich structures. A fragment of enlazin, enl-tr, was isolated as a genetic suppressor of the cytokinesis defect of cortexillin-I mutants. Expression of enl-tr disrupts expression of endogenous enlazin, indicating that enl-tr functions as a dominantnegative lesion. Enlazin is distributed globally during cytokinesis and is required for cortical tension and cell adhesion. Consistent with a role in cell mechanics, inhibition of enlazin in a cortexillin-I background restores cytokinesis furrowing dynamics and suppresses the growth-in-suspension defect. However, as expected for a role in cell adhesion, inhibiting enlazin in a myosin-II background induces a synthetic cytokinesis phenotype, frequently arresting furrow ingression at the dumbbell shape and/or causing recession of the furrow. Thus, enlazin has roles in cell mechanics and adhesion, and these roles seem to be differentially significant for cytokinesis, depending on the genetic background.

The multi-FERM-domain-containing protein FrmA is required for turnover of paxillin-adhesion sites during cell migration of Dictyostelium

“…S1A) of which, knockout studies have been carried out for FrmC, talinA, talinB and myosinVII (Niewohner et al, 1997;Octtaviani et al, 2006;Tsujioka et al, 1999;Tuxworth et al, 2001). Loss of talinA greatly reduces cell-substrate adhesion and this cannot be compensated for by the expression of talinB, suggesting a unique role for talinA in cell-substrate adhesion (Niewohner et al, 1997).…”

“…Taken together with the requirement of talinB for migration within a multicellular environment (Tsujioka et al, 2004), it suggests that Dictyostelium talins play a role in adhesion at the leading edge of cells undergoing cell migration. MyosinVII and FrmC have also been shown to play a role in the regulation of cell-substrate adhesion as loss of either, results in reduced cell-substrate adhesion (Octtaviani et al, 2006;Tuxworth et al, 2001). Indeed, talinA and myosinVII have been shown to bind to each other (Tuxworth et al, 2005).…”

Evidence that Noncoding RNA dutA Is a Multicopy Suppressor of Dictyostelium discoideum STAT Protein Dd-STATa

“…Library complementation using a cDNA expression library circumvents these issues by simplifying and accelerating gene identification and validation. Further, various types of genetic interactions are possible (overexpression, gain-of-function, dominant-negative, and attenuated functions), increasing the richness of the approach (14,35,40). Here, we describe the isolation of multicopy suppressor clones of Dd-STATa using this approach.…”

GBF-dependent family genes morphologically suppress the partially active Dictyostelium STATa strain

“…Library complementation using a complementary DNA (cDNA) expression library facilitates gene identification and validation. The latter technique also increases the richness of the approach because various genetic interactions can be included: overexpression, gain of function, dominant-negative and attenuated functions (Girard et al 2004;Octtaviani et al 2006;Robinson and Spudich 2000). Using this approach, we recently isolated multicopy suppressor clones of Dd-STATa, a functional homologue of metazoan signal transducers and activators of transcription (STAT) proteins (Shimada and Kawata 2007).…”