The Rho GTP exchange factor Lfc promotes spindle assembly in early mitosis.
Rho GTPases regulate reorganization of actin and microtubule cytoskeletal structures during both interphase and mitosis. The timing and subcellular compartment in which Rho GTPases are activated is controlled by the large family of Rho GTP exchange factors (RhoGEFs). Here, we show that the microtubule-associated RhoGEF Lfc is required for the formation of the mitotic spindle during prophase/prometaphase. The inability of cells to assemble a functioning spindle after Lfc inhibition resulted in a delay in mitosis and an accumulation of prometaphase cells. Inhibition of Lfc's primary target Rho GTPase during prophase/prometaphase, or expression of a catalytically inactive mutant of Lfc, also prevented normal spindle assembly and resulted in delays in mitotic progression. Coinjection of constitutively active Rho GTPase rescued the spindle defects caused by Lfc inhibition, suggesting the requirement of RhoGTP in regulating spindle assembly. Lastly, we implicate mDia1 as an important effector of Lfc signaling. These findings demonstrate a role for Lfc, Rho, and mDia1 during mitosis.
Department of Medical Biophysics, University of Toronto, 1 King's College Circle, Toronto, ON, Canada M5S 1A8.
Christopher J
CJ
Bakal
Dina
D
Finan
José
J
LaRose
Clark D
CD
Wells
Gerald
G
Gish
Sarang
S
Kulkarni
Paulo
P
DeSepulveda
Andrew
A
Wilde
Robert
R
Rottapel
D000818:Animals; D002460:Cell Line; D017931:DNA Primers; D019204:GTP-Binding Proteins / Q000235:genetics; D005822:Genetic Vectors; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008845:Microinjections; D008856:Microscopy, Fluorescence; D011418:Prophase / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D064067:Rho Guanine Nucleotide Exchange Factors; D008941:Spindle Apparatus / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism
C577402:Arhgef2 protein, mouse; D017931:DNA Primers; D020662:Guanine Nucleotide Exchange Factors; D011518:Proto-Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D019204:GTP-Binding Proteins; D020741:rho GTP-Binding Proteins