dictyNews

Electronic Edition

Volume 46, number 22

August 7, 2020



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Abstracts

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In Vivo Assembly of a Dictyostelium Lamin Mutant Induced by Light, 

Mechanical Stress, and pH



Marianne Grafe, Phillip Hofmann, Petros Batsios, Irene Meyer and 

Ralph Gräf *





Cells, in press 



We expressed Dictyostelium lamin (NE81) lacking both a functional 

nuclear localization signal and a CAAX-box for C-terminal lipid 

modification. This lamin mutant assembled into supramolecular, 

three-dimensional clusters in the cytosol that disassembled at the 

onset of mitosis and re-assembled in late telophase, thus mimicking 

the behavior of the endogenous protein. As disassembly is regulated 

by CDK1-mediated phosphorylation at serine 122, we generated a 

phosphomimetic S122E mutant called 

GFP-NE81-S122E-ΔNLSΔCLIM. Surprisingly, during imaging, the 

fusion protein assembled into cytosolic clusters, similar to the protein 

lacking the phosphomimetic mutation. Clusters disassembled again 

in darkness. Assembly could be induced with blue but not green or 

near ultraviolet light, and it was independent of the fusion tag. 

Assembly similarly occurred upon cell flattening. Earlier reports and 

own observations suggested that both blue light and cell flattening 

could result in a decrease of intracellular pH. Indeed, keeping the 

cells at low pH also reversibly induced cluster formation. Our results 

indicate that lamin assembly can be induced by various stress 

factors and that these are transduced via intracellular acidification. 

Although these effects have been shown in a phosphomimetic 

CDK1 mutant of the Dictyostelium lamin, they are likely relevant also 

for wild-type lamin.





submitted by: Ralph Gräf [[log in to unmask]]

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[End dictyNews, volume 46, number 22]