Efficient Endocytic Uptake and Maturation in Drosophila Oocytes Requires Dynamitin/p50.
Dynactin is a multi-subunit complex that functions as a regulator of the Dynein motor. A central component of this complex is Dynamitin/p50 (Dmn). Dmn is required for endosome motility in mammalian cell lines. However, the extent to which Dmn participates in the sorting of cargo via the endosomal system is unknown. In this study, we examined the endocytic role of Dmn using the Drosophila melanogaster oocyte as a model. Yolk proteins are internalized into the oocyte via clathrin-mediated endocytosis, trafficked through the endocytic pathway, and stored in condensed yolk granules. Oocytes that were depleted of Dmn contained fewer yolk granules than controls. In addition, these oocytes accumulated numerous endocytic intermediate structures. Particularly prominent were enlarged endosomes that were relatively devoid of Yolk proteins. Ultrastructural and genetic analyses indicate that the endocytic intermediates are produced downstream of Rab5. Similar phenotypes were observed upon depleting Dynein heavy chain (Dhc) or Lis1. Dhc is the motor subunit of the Dynein complex and Lis1 is a regulator of Dynein activity. We therefore propose that Dmn performs its function in endocytosis via the Dynein motor. Consistent with a role for Dynein in endocytosis, the motor colocalized with the endocytic machinery at the oocyte cortex in an endocytosis-dependent manner. Our results suggest a model whereby endocytic activity recruits Dynein to the oocyte cortex. The motor along with its regulators, Dynactin and Lis1, functions to ensure efficient endocytic uptake and maturation.
Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia.
Guojun
G
Liu
Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia.
Paulomi
P
Sanghavi
James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia.
Kathryn E
KE
Bollinger
Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia.
Libby
L
Perry
Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia.
Brendan
B
Marshall
Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia.
Penny
P
Roon
Department of Germline Development, Division of Organogenesis, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan.
Tsubasa
T
Tanaka
Department of Germline Development, Division of Organogenesis, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan.
Akira
A
Nakamura
Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia ggonsalvez@gru.edu.
Graydon B
GB
Gonsalvez
D000818:Animals; D003599:Cytoskeleton / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster; D000072159:Dynactin Complex; D004398:Dyneins / Q000096:biosynthesis / Q000235:genetics; D004705:Endocytosis / Q000235:genetics*; D011992:Endosomes / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism*; D021381:Protein Transport / Q000235:genetics
D029721:Drosophila Proteins; D000072159:Dynactin Complex; C513192:Lis-1 protein, Drosophila; D008869:Microtubule-Associated Proteins; D004398:Dyneins
cell polarity; dynactin; endocytosis; kinesin; microtubule motors