SNX4 in complex with clathrin and dynein: implications for endosome movement.
BACKGROUND
Sorting nexins (SNXs) constitute a family of proteins classified by their phosphatidylinositol (PI) binding Phox homology (PX) domain. Some members regulate intracellular trafficking. We have here investigated mechanisms underlying SNX4 mediated endosome to Golgi transport.


RESULTS
We show that SNX4 forms complexes with clathrin and dynein. The interactions were inhibited by wortmannin, a PI3-kinase inhibitor, suggesting that they form when SNX4 is associated with PI(3)P on endosomes. We further localized the clathrin interacting site on SNX4 to a clathrin box variant. A short peptide containing this motif was sufficient to pull down both clathrin and dynein. Knockdown studies demonstrated that clathrin is not required for the SNX4/dynein interaction. Moreover, clathrin knockdown led to increased Golgi transport of the toxin ricin, as well as redistribution of endosomes.


CONCLUSIONS
We discuss the possibility of clathrin serving as a regulator of SNX4-dependent transport. Upon clathrin release, dynein may bind SNX4 and mediate retrograde movement.
Skånland
Sigrid S
SS
Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.
Wälchli
Sébastien
S
Brech
Andreas
A
Sandvig
Kirsten
K
D000730:Androstadienes / Q000494:pharmacology; D002460:Cell Line; D002966:Clathrin / Q000737:chemistry*; D004398:Dyneins / Q000737:chemistry*; D011992:Endosomes / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006056:Golgi Apparatus / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D018613:Microscopy, Confocal / Q000379:methods; D008954:Models, Biological; D011485:Protein Binding; D021381:Protein Transport; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D000077191:Wortmannin
D000730:Androstadienes; D002966:Clathrin; D004791:Enzyme Inhibitors; C513981:SNX4 protein, human; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D004398:Dyneins; D000077191:Wortmannin