Contractile Vacuole Complex—Its Expanding Protein Inventory - International Review of Cell and Molecular Biology - page 382

Table 9.3 Effects of gene silencing on the CVC of Paramecium — cont'd
Component Effect Reference

F-SUs Similar effect Wassmer

et al. (2005)

a2 SUs CV swelling, cell death Wassmer

et al. (2006)

a3 SUs No effect Wassmer

et al. (2006)

Stomatin4 Accelerated CV pumping Reuter et al.

(2013)

a Restricted viability within 30 min exposure to increased [Ca 2 þ ] o , from 1 to 5 mM.
b Immediate loss of viability within 2 min exposure to increased [Ca 2 þ ] o , from 1 to 5 mM.

3.2.4 Stomatin and mechanosensitive Ca 2þ channels
Among a plethora of mechanosensitive ion channels are transient receptor
potential (TRP)- and Piezo-type proteins ( Delmas et al., 2011; Xiao and
Xu, 2010 ). The Paramecium DB does contain orthologs of Piezo,
mechanosensitive channels in mammals ( Coste et al., 2010 ), as well as
TRP channels, as summarized by Plattner et al. (2012) . As known from
other cells, some of the latter are sensitive to membrane stretch ( Kung
et al., 2010 ) and may occur partly in the cell membrane and partly in some
organelles ( Patel and Docampo, 2010 ).
The tension measured on the Paramecium CV ( Sugino et al., 2005 )is
compatible with that required for activation of such channels ( Kung
et al., 2010 ). Mechanosensitive channels are likely to occur in the Parame-
cium CVC for the following reasons, although this remains hypothetic for
the time being. (i) We find the scaffolding protein, Stomatin, subfamily 4
associated with the CVC ( Reuter et al., 2013 ). Stomatin homologs are
found from bacteria ( Hinderhofer et al., 2009 ) up to man ( Lapatsina
et al., 2012 ), and they are known to serve for the positioning of
mechanosensitive Ca 2 þ channels in a variety of systems, including
Med1 in C. elegans where it associates with the Stomatin homolog Mec-2
( Huang et al., 1995 ). (ii) The Paramecium database contains a
mechanosensitive Ca 2 þ -channel type Piezo ( Coste et al., 2010 ), but its char-
acterization and localization are still open. Ca 2 þ released by these or any
other CRCs could contribute, for instance, to the rhythmic fusion processes