Phosphatidylinositol 4-Kinase IIIβ Regulates the Transport of Ceramide between the Endoplasmic Reticulum and Golgi

• Published in: The Journal of biological chemistry Vol. 281; no. 47; pp. 36369 - 36377
• Main Authors: Tóth, Balázs, Balla, András, Ma, Hui, Knight, Zachary A., Shokat, Kevan M., Balla, Tamas
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 24.11.2006; American Society for Biochemistry and Molecular Biology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M604935200

The recently identified ceramide transfer protein, CERT, is responsible for the bulk of ceramide transport from the endoplasmic reticulum (ER) to the Golgi. CERT has a C-terminal START domain for ceramide binding and an N-terminal pleck-strin homology domain that binds phosphatidylinositol 4-phosphate suggesting that phosphatidylinositol (PI) 4-kinases are involved in the regulation of CERT-mediated ceramide transport. In the present study fluorescent analogues were used to follow the ER to Golgi transport of ceramide to determine which of the four mammalian PI 4-kinases are involved in this process. Overexpression of pleckstrin homology domains that bind phosphatidylinositol 4-phosphate strongly inhibited the transport of C5-BODIPY-ceramide to the Golgi. A newly identified PI 3-kinase inhibitor, PIK93 that selectively inhibits the type III PI 4-kinase β enzyme, and small interfering RNA-mediated down-regulation of the individual PI 4-kinase enzymes, revealed that PI 4-kinase β has a dominant role in ceramide transport between the ER and Golgi. Accordingly, inhibition of PI 4-kinase III β either by wortmannin or PIK93 inhibited the conversion of [3H]serine-labeled endogenous ceramide to sphingomyelin. Therefore, PI 4-kinase β is a key enzyme in the control of spingomyelin synthesis by controlling the flow of ceramide from the ER to the Golgi compartment.