Paramecium - Deutsche Gesellschaft für Protozoologie / German ...

Protein phosphatase 2B (PP2B, calcineurin) in Paramecium
Ivonne M.Sehring 1 , Dean Fraga 2 , Roland Kissmehl 1 , Martina Reis 1 ,
Robert Hinrichsen 3 , Helmut Plattner 1
1 Universität Konstanz
2 College of Wooster
3 Indiana University of Pennsylvania
Protein phosphatase 2B (PP2B) or calcineurin (CaN) is a Ser/Thr
phosphatase consisting of two subunits, the catalytic, calmodulin-
(CaM-) binding CaN-A subunit and the regulatory Ca 2+ -binding CaN-
B subunit. Based on the Paramecium genome project, we could identify
7 subfamilies of the CaN-A subunit and one subfamily of the
CaN-B subunit, each subfamily with two members of considerable
identity on the amino acid level ( >55 between, and >94% within subfamilies).
Within CaN-A subfamily members, the catalytic domain
and the CaN-B binding region are maximally preserved and their molecular
modeling resulted in a 3D structure almost identical to a human
ortholog. Overall similarities of CaN-A and CaN-B to orthologs
from other organisms are between 41 and 54 %. Heterologous expression
in E. coli and Western blot analysis resulted in binding of established,
specific antibodies against the mammalian subunits. Silencing
of the CaN-A1 gene resulted in a reduction of stimulated trichocyst
exocytosis just as with the “non-discharge” mutant nd7. Although
silencing also affects Ca 2+ dynamics upon exocytosis stimulation, the
underlying mechanism and its effect on trichocyst release remains to
be established.
ivonne.sehring@uni-konstanz.de
dfraga@acs.wooster.edu
roland.kissmehl@uni-konstanz.de
martina.reiss@uni-konstanz.de
bhinrich@iup.edu
helmut.plattner@uni-konstanz.de
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