SUNDAY, DECEMBER 4- Late Abstracts 1 - Molecular Biology of the ...

SUNDAY
the establishment of ciliary identity in Giardia intestinalis. Our candidate approach focuses on
three NEK kinases. NEK kinases were first identified for their role in mitosis but have been
shown to play a role in ciliogenesis and flagellar length determination in model systems such as
Tetrahymena (2,3). Similar to the Tetrahymena genome, the giardial genome encodes an
unusually large number of these kinases, suggesting that some may have non-mitotic,
regulatory roles. Consistent with this hypothesis, we have identified several putative NEK
kinases associated with the giardial ventral disk and flagella. Most of these are predicted to be
catalytically inactive and may play structural or kinase activity independent regulatory roles.
Three of the kinases, GL50803_11311, _8445, and _95593, however, contain a canonical
kinase active site. We are using morpholino knockdown as well as overexpression of kinaseinactive
and constitutively active variants to assess whether these putative kinases contribute to
Giardia motility and/or ciliogenesis.
References:
1. Dawson SC and House SA (2010) Methods Cell Biol.
2. Quarmby LM and Mahjoub MR (2005) J Cell Sci.
3. Wloga D, et al (2006) Mol Biol Cell.
1991
Trophic accumulation of the antidepressant sertraline/Zoloft in fungal secretory
membranes.
E. Perlstein 1 , J. Chen 1 , D. Korostyshevsky 1 ; 1 Lewis-Sigler Institute/Princeton University,
Princeton, NJ
Many antidepressants are cationic amphipaths, which spontaneously accumulate in cellular
membranes in the absence of their protein targets. However, the clinical relevance of
progressive cellular membrane infiltration by antidepressants in humans is poorly understood.
Here we take an “evolutionary pharmacology” approach to studying the effects of the selectiveserotonin
reuptake inhibitor sertraline/Zoloft on cellular membrane homeostasis in the simple
eukaryote Saccharomyces cerevisiae, which lacks a serotonin transporter entirely. We
biochemically characterized the association of tritiated sertraline with the membranes of the
fungal secretory pathway, and in parallel performed a quantitative ultrastructural analysis of
membrane quality control in untreated vs. sertraline-treated cells. These experiments have
revealed that sertraline enters yeast cells and then reshapes the secretory pathway by a
complex process. Internalization of the neutral species proceeds by simple diffusion amplified
by lysosomotropism, but is counteracted by ATP-dependent xenobiotic efflux. At equilibrium, a
small fraction (10-15%) of spontaneously reprotonated sertraline is soluble while the remainder
partitions into secretory pathway membranes by both adsorption and intercalation. Asymmetric
accumulation of sertraline results in concentration- and time-dependent local membrane
curvature stresses, which in turn trigger an adaptive autophagy-dependent relief response. Our
model appears to support the notion of a serotonin transporter-independent, “amphipath
accumulation” component of antidepressant pharmacology in humans.
1992
The UBX-domain-containing protein Ubx2/ Ubxd8 regulates lipid droplet homeostasis.
C-W. Wang 1 , S-C. Lee 1 ; 1 Institute of Plant and Microbial Biology, Academia Sinica, Nankang,
Taipei, Taiwan
Lipid droplets (LDs) are central organelles for maintaining lipid homeostasis. However, how cells
control the size and number of LDs remains largely unknown. Herein, we report that Ubx2, a
protein involved in endoplasmic reticulum (ER)-associated degradation (ERAD), is crucial for LD