Heine, MartinMartinHeineCramm-Behrens, Catharina ICatharina ICramm-BehrensAnsari, AtharAtharAnsariHSUEH-PING CHURyazanov, Alexey GAlexey GRyazanovNaim, Hassan YHassan YNaimJacob, RalfRalfJacob2019-09-182019-09-182005-07-080021-9258https://scholars.lib.ntu.edu.tw/handle/123456789/424755A key aspect in the structure of epithelial cells is the maintenance of a polarized organization based on a highly specific sorting machinery for cargo destined for the apical or the basolateral membrane domain at the exit site of the trans-Golgi network. We could recently identify two distinct post-trans-Golgi network vesicle populations that travel along separate routes to the plasma membrane, a lipid raft-dependent and a lipid raft-independent pathway. A new component of raft-carrying apical vesicles is alpha-kinase 1 (ALPK1), which was identified in immunoisolated vesicles carrying raft-associated sucrase-isomaltase (SI). This kinase was absent from vesicles carrying raft-non-associated lactase-phlorizin hydrolase. The expression of ALPK1 increases by the time of epithelial cell differentiation, whereas the intracellular localization of ALPK1 on apical transport vesicles was confirmed by confocal analysis. A phosphorylation assay on isolated SI-carrying vesicles revealed the phosphorylation of a protein band of about 105 kDa, which could be identified as the motor protein myosin I. Finally, a specific reduction of ALPK1-expression by RNA interference results in a significant decrease in the apical delivery of SI. Taken together, our data suggest that the phosphorylation of myosin I by ALPK1 is an essential process in the apical trafficking of raft-associated SI.enjournal article10.1074/jbc.M502265200158831612-s2.0-21844442358https://api.elsevier.com/content/abstract/scopus_id/21844442358