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J. Cell Biol.,
Volume 143, Number 3, November 2, 1998 795-813
* Institut für Physiologische Chemie, and We report the identification and initial characterization of paralemmin, a putative new morphoregulatory protein associated with the plasma membrane.
Paralemmin is highly expressed in the brain but also
less abundantly in many other tissues and cell types.
cDNAs from chicken, human, and mouse predict acidic
proteins of 42 kD that display a pattern of sequence
cassettes with high inter-species conservation separated
by poorly conserved linker sequences. Prenylation and
palmitoylation of a COOH-terminal cluster of three
cysteine residues confers hydrophobicity and membrane association to paralemmin. Paralemmin is also
phosphorylated, and its mRNA is differentially spliced
in a tissue-specific and developmentally regulated manner. Differential splicing, lipidation, and phosphorylation contribute to electrophoretic heterogeneity that
results in an array of multiple bands on Western blots,
most notably in brain. Paralemmin is associated with
the cytoplasmic face of the plasma membranes of
postsynaptic specializations, axonal and dendritic processes and perikarya, and also appears to be associated
with an intracellular vesicle pool. It does not line the
neuronal plasmalemma continuously but in clusters and patches. Its molecular and morphological properties
are reminiscent of GAP-43, CAP-23, and MARCKS,
proteins implicated in plasma membrane dynamics.
Overexpression in several cell lines shows that paralemmin concentrates at sites of plasma membrane activity such as filopodia and microspikes, and induces
cell expansion and process formation. The lipidation
motif is essential for this morphogenic activity. We propose a function for paralemmin in the control of cell
shape, e.g., through an involvement in membrane flow
or in membrane-cytoskeleton interaction.
Institut für Anatomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
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