tailieunhanh - Báo cáo khoa học: The stop transfer sequence of the human UDPglucuronosyltransferase 1A determines localization to the endoplasmic reticulum by both static retention and retrieval mechanisms

Human UDP-glucuronosyltransferase 1A (UGT1A) isoforms are endoplas-mic reticulum (ER)-resident type I membrane proteins responsible for the detoxification of a broad range of toxic phenolic compounds. These pro-teins contain a C-terminal stop transfer sequence with a transmembrane domain (TMD), which anchors the protein into the membrane, followed by a short cytosolic tail (CT). | ềFEBS Journal The stop transfer sequence of the human UDP-glucuronosyltransferase 1A determines localization to the endoplasmic reticulum by both static retention and retrieval mechanisms Lydia Barre Jacques Magdalou Patrick Netter Sylvie Fournel-Gigleux and Mohamed Ouzzine UMR 7561 CNRS-Universite Henri Poincare Nancy I France Keywords endoplasmic reticulum retention membrane protein stop transfer sequence transmembrane domain UDP-glucuronosyltransferase Correspondence M. Ouzzine UMR CNRS 7561-Universite Henri Poincare Nancy 1 Faculte de Medecine BP 184 54505 Vandreuvre-les-Nancy France Fax 33 3 83 68 39 59 Tel 33 3 83 68 39 72 E-mail ouzzine@ Received 12 October 2004 revised 16 December 2004 accepted 24 December 2004 doi Human UDP-glucuronosyltransferase 1A UGT1A isoforms are endoplasmic reticulum ER -resident type I membrane proteins responsible for the detoxification of a broad range of toxic phenolic compounds. These proteins contain a C-terminal stop transfer sequence with a transmembrane domain TMD which anchors the protein into the membrane followed by a short cytosolic tail CT . Here we investigated the mechanism of ER residency of UGT1A mediated by the stop transfer sequence by analysing the subcellular localization and sensitivity to endoglycosidases of chimeric proteins formed by fusion of UGT1A stop transfer sequence TMD CT with the ectodomain of the plasma membrane CD4 reporter protein. We showed that the stop transfer sequence when attached to C-terminus of the CD4 ectodomain was able to prevent it from being transported to the cell surface. The protein was retained in the ER indicating that this sequence functions as an ER localization signal. Furthermore we demonstrated that ER localization conferred by the stop transfer sequence was mediated in part by the KSKTH retrieval signal located on the CT. Interestingly our data indicated that UGT1A TMD alone was sufficient to retain the protein in ER .