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J. Cell Biol.,
Volume 145, Number 1, April 5, 1999 167-181
* A.-Butenandt-Institut für Zellbiologie, Ludwig-Maximilians-Universität, 80336 München, Germany; and 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.
Institut für
Biochemie I, Universität zu Köln, 50931 Köln, Germany
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