Maria Isabel Geli

PhD 1993 University of Barcelona, Barcelona, Sp ain,
Postdocto ral work at th e Bioze ntrum of the University of
Basel, Basel,Switze rland,
Group leader at the Bioch emie Zentrum (BZH),
University of Heidelberg, since 1999

Current Research
Endocytosis is the process whereby cells
internalize part of their own plasma
membrane engulfing extracellular solutes.
Different mechanism of endocytosis serve
fundamental cellular functions such as the
immune response, the uptake of nutrients,
the downregulation of hormone receptors or
the regeneration of synaptic vesicles. The
molecular mechanisms underlying some of
these pathways are largely unknown. Our
aim is to identify proteins required for the
uptake step of endocytosis using the yeast
S.cerevisiae as a model system. In yeast,
endocytosis seems to be dependent on two
actin-dependent motor systems: the
unconventional myosins-I and the ARP2/3
actin-nucleating complex. Our results suggest
that in response to intracellular signals
myosins-I are recruited to the plasma
membrane where they promote ARP2/3-
dependent actin polymerization. Our current
hypothesis postulates that a transient actin
coat is built at the inner surface of the lipid
bilayer. The myosin motor head might then
help to remodel the coat and form the primary
endocytic profile. Understanding in detail how
myosins-I are recruited to the plasma
membrane, w hat i s the m olecular machinery
involved in myosin-I-induced actin
polymerization and how is hydrolysis of ATP
coupled to deformation of the lipid bilayer are
our immediate research goals.

Maria Isabel Geli
Biochemie Zentrum (BZH)
Im Neuenheimer Feld 328
69120 Heidelberg
Tel: - 49 - 6221 - 54 5 4 23
Fax: - 49 - 6221 - 54 4 3 69
person al home page: /zentral/b zh/geli.html

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Ph D student project
How are the yeast myosins-I recruited to the
plasma membrane?
Myosins-I are ubiquitous actin-dependent
molecular motors that bear a short tail that binds
acidic phospholipids. A number of experiments
demonstrate that myosins-I shuffle between the
cytosol and specific subdomains of the plasma
membrane where they fulfill their cellular task.
What are the cis and trans elements required to
achieve this particular distribution is unknown.
We have established a novel reporter system to
directly sense the plasma membrane/myosins-I
interaction using a simple plate assay. With this
tool in hands, we would like to perform genetic
screens to isolate intragenic and extragenic
mutations that disturb such interaction. Once
putative cis and trans elements w ere identified,
we would further analyze their role in
determining the subcellular distribution of the
myosins-I using immunoflurescence and
biochemistry. Finally, the functional relevance of
the elements identified would be tested by
investigating their requirement for endocytosis.

Selected Publications
Research articles on the topic
Munn et al. (1995) Mol Biol Cell 6, 1721-1742.
Geli and Riezman (1996) Science, 272, 533-535.
Geli et al. (1998) EMBO J. 17, 635-647.
Geli et al. (2000) EMBO J. 19, 4281-91.
Geli and Riezman (1998) J. Cell Sci. 111, 1031-1037.





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