Clathrin heavy chain plays multiple roles in polarizing the Drosophila oocyte downstream of Bic-D.
Bicaudal-D (Bic-D), Egalitarian (Egl), microtubules and their motors form a transport machinery that localizes a remarkable diversity of mRNAs to specific cellular regions during oogenesis and embryogenesis. Bic-D family proteins also promote dynein-dependent transport of Golgi vesicles, lipid droplets, synaptic vesicles and nuclei. However, the transport of these different cargoes is still poorly understood. We searched for novel proteins that either mediate Bic-D-dependent transport processes or are transported by them. Clathrin heavy chain (Chc) co-immunopurifies with Bic-D in embryos and ovaries, and a fraction of Chc colocalizes with Bic-D. Both proteins control posterior patterning of the Drosophila oocyte and endocytosis. Although the role of Chc in endocytosis is well established, our results show that Bic-D is also needed for the elevated endocytic activity at the posterior of the oocyte. Apart from affecting endocytosis indirectly by its role in osk mRNA localization, Bic-D is also required to transport Chc mRNA into the oocyte and for transport and proper localization of Chc protein to the oocyte cortex, pointing to an additional, more direct role of Bic-D in the endocytic pathway. Furthermore, similar to Bic-D, Chc also contributes to proper localization of osk mRNA and to oocyte growth. However, in contrast to other endocytic components and factors of the endocytic recycling pathway, such as Rabenosyn-5 (Rbsn-5) and Rab11, Chc is needed during early stages of oogenesis (from stage 6 onwards) to localize osk mRNA correctly. Moreover, we also uncovered a novel, presumably endocytosis-independent, role of Chc in the establishment of microtubule polarity in stage 6 oocytes.
Institute of Cell Biology, University of Bern, 3012 Berne, Switzerland.
Paula
P
Vazquez-Pianzola
Jacqueline
J
Adam
Dominique
D
Haldemann
Daniel
D
Hain
Henning
H
Urlaub
Beat
B
Suter
D000818:Animals; D019521:Body Patterning / Q000235:genetics; D016764:Cell Polarity / Q000235:genetics; D033922:Clathrin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D002999:Clone Cells; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D004705:Endocytosis / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D008954:Models, Biological; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism; D009866:Oogenesis / Q000235:genetics; D010053:Ovary / Q000166:cytology / Q000378:metabolism; D021381:Protein Transport; D034443:RNA Transport / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
C061998:BicD protein, Drosophila; C000588864:Chc protein, Drosophila; D029721:Drosophila Proteins; D012333:RNA, Messenger; C091675:osk protein, Drosophila; D033922:Clathrin Heavy Chains; D049452:Green Fluorescent Proteins
Clathrin heavy chain; Drosophila oogenesis; Germ line; Microtubules; Polarity formation; RNA localization