Genes that cause aberrant cell morphology by overexpression in fission yeast: a role of a small GTP-binding protein Rho2 in cell morphogenesis

To identify the genes involved in cell morphogenesis in Schizosaccharomyces pombe, we screened for the genes that cause aberrant cell morphology by overexpression. The isolated genes were classified on the basis of morphology conferred. One of the genes causing a rounded morphology was identified as the rho2+ gene encoding a small GTP-binding protein. The overexpression of rho2+ resulted in a randomized distribution of cortical F-actin and formation of a thick cell wall. Analyses using cdc mutants suggested that the overexpression of rho2+ prevents the establishment of growth polarity in G1. The rho2+ gene was not essential, but among cells deleted for rho2+, those with an irregular shape were observed. The disruptant also showed a defect in cell wall integrity. An HA-Rho2 expressed in the cell was suggested to be present as a membrane-bound form by a cell fractionation experiment. A GFP-Rho2 was localized at the growing end(s) of the cell and the septation site. The localization of GFP-Rho2 during interphase was partially dependent on sts5+. These results indicate that Rho2 is involved in cell morphogenesis, control of cell wall integrity, control of growth polarity, and maintenance of growth direction. Analysis of functional overlapping between Rho2 and Rho1 revealed that their functions are distinct from each other, with partial overlapping.

Download Full-text

A GTP-binding protein regulates the activity of (1–>3)-beta-glucan synthase, an enzyme directly involved in yeast cell wall morphogenesis.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)47418-2 ◽

1994 ◽

Vol 269 (49) ◽

pp. 31267-31274

Author(s):

P C Mol ◽

H M Park ◽

J T Mullins ◽

E Cabib

Keyword(s):

Cell Wall ◽

Yeast Cell ◽

Binding Protein ◽

Yeast Cell Wall ◽

Beta Glucan ◽

Gtp Binding Protein ◽

Glucan Synthase ◽

Gtp Binding ◽

Cell Wall Morphogenesis

Download Full-text

Small GTP-binding Protein RalA Associates with Weibel-Palade Bodies in Endothelial Cells

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614349 ◽

1999 ◽

Vol 82 (09) ◽

pp. 1177-1181 ◽

Cited By ~ 27

Author(s):

Hubert de Leeuw ◽

Pauline Wijers-Koster ◽

Jan van Mourik ◽

Jan Voorberg

Keyword(s):

Endothelial Cells ◽

Binding Proteins ◽

Binding Protein ◽

Control Release ◽

Small Gtpase ◽

Gtp Binding Protein ◽

Two Dimensional Gel Electrophoresis ◽

Gtp Binding Proteins ◽

Dense Granules ◽

Gtp Binding

SummaryIn endothelial cells von Willebrand factor (vWF) and P-selectin are stored in dense granules, so-called Weibel-Palade bodies. Upon stimulation of endothelial cells with a variety of agents including thrombin, these organelles fuse with the plasma membrane and release their content. Small GTP-binding proteins have been shown to control release from intracellular storage pools in a number of cells. In this study we have investigated whether small GTP-binding proteins are associated with Weibel-Palade bodies. We isolated Weibel-Palade bodies by centrifugation on two consecutive density gradients of Percoll. The dense fraction in which these subcellular organelles were highly enriched, was analysed by SDS-PAGE followed by GTP overlay. A distinct band with an apparent molecular weight of 28,000 was observed. Two-dimensional gel electrophoresis followed by GTP overlay revealed the presence of a single small GTP-binding protein with an isoelectric point of 7.1. A monoclonal antibody directed against RalA showed reactivity with the small GTP-binding protein present in subcellular fractions that contain Weibel-Palade bodies. The small GTPase RalA was previously identified on dense granules of platelets and on synaptic vesicles in nerve terminals. Our observations suggest that RalA serves a role in regulated exocytosis of Weibel-Palade bodies in endothelial cells.

Download Full-text

Rap1b Association with the Platelet Cytoskeleton Occurs in the Absence of Glycoproteins IIb/IIIa

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615073 ◽

1998 ◽

Vol 79 (04) ◽

pp. 832-836 ◽

Cited By ~ 3

Author(s):

Thomas Fischer ◽

Christina Duffy ◽

Gilbert White

Keyword(s):

Molecular Weight ◽

Divalent Cation ◽

Binding Proteins ◽

Binding Protein ◽

Platelet Membrane ◽

Low Molecular Weight ◽

Membrane Glycoproteins ◽

Gtp Binding Protein ◽

Gtp Binding Proteins ◽

Gtp Binding

SummaryPlatelet membrane glycoproteins (GP) IIb/IIIa and rap1b, a 21 kDa GTP binding protein, associate with the triton-insoluble, activation-dependent platelet cytoskeleton with similar rates and divalent cation requirement. To examine the possibility that GPIIb/IIIa was required for rap1b association with the cytoskeleton, experiments were performed to determine if the two proteins were linked under various conditions. Chromatography of lysates from resting platelets on Sephacryl S-300 showed that GPIIb/IIIa and rap1b were well separated and distinct proteins. Immunoprecipitation of GPIIb/IIIa from lysates of resting platelets did not produce rap1b or other low molecular weight GTP binding proteins and immunoprecipitation of rap1b from lysates of resting platelets did not produce GPIIb/IIIa. Finally, rap1b was associated with the activation-dependent cytoskeleton of platelets from a patient with Glanzmann’s thrombasthenia who lacks surface expressed glycoproteins IIb and IIIa. Based on these findings, we conclude that no association between GPIIb/IIIa and rap1b is found in resting platelets and that rap1b association with the activation-dependent cytoskeleton is at least partly independent of GPIIb/IIIa.

Download Full-text