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Identification of a Suppressor of the Dictyostelium Profilin-Minus Phenotype as a CD36/LIMP-II Homologue

Iakowos Karakesisoglou, Klaus-Peter Janssen, Ludwig Eichinger, Angelika A. Noegel and Michael Schleicher
The Journal of Cell Biology
Vol. 145, No. 1 (Apr. 5, 1999), pp. 167-181
Stable URL: http://www.jstor.org/stable/1619209
Page Count: 15
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Identification of a Suppressor of the Dictyostelium Profilin-Minus Phenotype as a CD36/LIMP-II Homologue
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Abstract

Profilin is an ubiquitous G-actin binding protein in eukaryotic cells. Lack of both profilin isoforms in Dictyostelium discoideum resulted in impaired cytokinesis and an arrest in development. A restriction enzyme-mediated integration approach was applied to profilin-minus cells to identify suppressor mutants for the developmental phenotype. A mutant with wild-type-like development and restored cytokinesis was isolated. The gene affected was found to code for an integral membrane glycoprotein of a predicted size of 88 kD containing two transmembrane domains, one at the NH2 terminus and the other at the COOH terminus. It is homologous to mammalian CD36/LIMP-II and represents the first member of this family in D. discoideum, therefore the name DdLIMP is proposed. Targeted disruption of the lmpA gene in the profilin-minus background also rescued the mutant phenotype. Immunofluorescence revealed a localization in vesicles and ringlike structures on the cell surface. Partially purified DdLIMP bound specifically to PIP2 in sedimentation and gel filtration assays. A direct interaction between DdLIMP and profilin could not be detected, and it is unclear how far upstream in a regulatory cascade DdLIMP might be positioned. However, the PIP2 binding of DdLIMP points towards a function via the phosphatidylinositol pathway, a major regulator of profilin.

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