Type II phosphatidylinositol 4-kinase regulates trafficking of secretory granule proteins in Drosophila.
Type II phosphatidylinositol 4-kinase (PI4KII) produces the lipid phosphatidylinositol 4-phosphate (PI4P), a key regulator of membrane trafficking. Here, we generated genetic models of the sole Drosophila melanogaster PI4KII gene. A specific requirement for PI4KII emerged in larval salivary glands. In PI4KII mutants, mucin-containing glue granules failed to reach normal size, with glue protein aberrantly accumulating in enlarged Rab7-positive late endosomes. Presence of PI4KII at the Golgi and on dynamic tubular endosomes indicated two distinct foci for its function. First, consistent with the established role of PI4P in the Golgi, PI4KII is required for sorting of glue granule cargo and the granule-associated SNARE Snap24. Second, PI4KII also has an unforeseen function in late endosomes, where it is required for normal retromer dynamics and for formation of tubular endosomes that are likely to be involved in retrieving Snap24 and Lysosomal enzyme receptor protein (Lerp) from late endosomes to the trans-Golgi network. Our genetic analysis of PI4KII in flies thus reveals a novel role for PI4KII in regulating the fidelity of granule protein trafficking in secretory tissues.
Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, M5G 1L7, Canada.
Jason
J
Burgess
Lauren M
LM
Del Bel
Cheng-I J
CI
Ma
Barbara
B
Barylko
Gordon
G
Polevoy
Janet
J
Rollins
Joseph P
JP
Albanesi
Helmut
H
Krämer
Julie A
JA
Brill
D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D005967:Glue Proteins, Drosophila / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D021381:Protein Transport; D012469:Salivary Glands / Q000254:growth & development / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
D029721:Drosophila Proteins; D005967:Glue Proteins, Drosophila; D008164:Luminescent Proteins; D000090802:rab7 GTP-Binding Proteins; D019870:1-Phosphatidylinositol 4-Kinase; D020691:rab GTP-Binding Proteins