Structural Basis for the Golgi Association by the Pleckstrin Homology Domain of the Ceramide Trafficking Protein (CERT)

From the Graduate School of Pharmaceutical Sciences, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033.
Journal of Biological Chemistry (Impact Factor: 4.57). 08/2012; 287(40):33706-18. DOI: 10.1074/jbc.M112.367730
Source: PubMed


Ceramide transport from the endoplasmic reticulum to the Golgi apparatus is crucial in sphingolipid biosynthesis, and the
process relies on the ceramide trafficking protein (CERT), which contains pleckstrin homology (PH) and StAR-related lipid
transfer domains. The CERT PH domain specifically recognizes phosphatidylinositol 4-monophosphate (PtdIns(4)P), a characteristic
phosphoinositide in the Golgi membrane, and is indispensable for the endoplasmic reticulum-to-Golgi transport of ceramide
by CERT. In this study, we determined the three-dimensional structure of the CERT PH domain by using solution NMR techniques.
The structure revealed the presence of a characteristic basic groove near the canonical PtdIns(4)P recognition site. An extensive
interaction study using NMR and other biophysical techniques revealed that the basic groove coordinates the CERT PH domain
for efficient PtdIns(4)P recognition and localization in the Golgi apparatus. The notion was also supported by Golgi mislocalization
of the CERT mutants in living cells. The distinctive binding modes reflect the functions of PH domains, as the basic groove
is conserved only in the PH domains involved with the PtdIns(4)P-dependent lipid transport activity but not in those with
the signal transduction activity.

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    • "Ceramide transfer protein (CERT) is responsible for the active transport of majority of the ceramide from ER to the Golgi complex where ceramide is converted to sphingomyelin and other complex sphingolipids [4]. CERT is a cytosolic protein that interacts with both ER and Golgi components to facilitate ceramide transfer [5], [6], [7], [8], [9]. "
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    • "The effect of PtdIns(4)P was overridden by increasing the concentration of UDP-glucose in the reaction solution, suggesting that PtdIns(4)P may inhibit contact between the active site of UGCG and UDP-glucose (Fig. 3). The interaction between PtdIns(4)P and the PH domain of CERT is indispensable for the transport of ceramide from ER to Golgi [50]. Therefore, CERT-transported ceramide may colocalize with PtdIns(4)P, thereby inhibiting, or interrupting, transfer of glucose from UDPglucose to ceramide by UGCG (Fig. 3). "
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    • "However, in the presence of phosphatidylserine, it exhibits stronger and more specific interaction over other differently phosphorylated PIPs (Hamard-Peron et al., 2010). Similar behavior, i.e., preferential and stronger binding of a chosen phosphoinositide in the presence of other phospholipids, mostly in the form of micelles was also described for proteins bearing pleckstrin homology domain (Sugiki et al., 2012). An important role of different phospholipids for the interaction of HIV-1 MA with the PM has been proposed recently by Vlach and Saad (2013). "
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