The class II phosphoinositide 3-kinase C2alpha is activated by clathrin and regulates clathrin-mediated membrane trafficking.
Phosphoinositides play key regulatory roles in vesicular transport pathways in eukaryotic cells. Clathrin-mediated membrane trafficking has been shown to require phosphoinositides, but little is known about the enzyme(s) responsible for their formation. Here we report that clathrin functions as an adaptor for the class II PI 3-kinase C2alpha (PI3K-C2alpha), binding to its N-terminal region and stimulating its catalytic activity, especially toward phosphorylated inositide substrates. Further, we show that endogenous PI3K-C2alpha is localized in coated pits and that exogenous expression affects clathrin-mediated endocytosis and sorting in the trans-Golgi network. These findings provide a mechanistic basis for localized inositide generation at sites of clathrin-coated bud formation, which, with recruitment of inositide binding proteins and subsequent synaptojanin-mediated phosphoinositide hydrolysis, may regulate coated vesicle formation and uncoating.
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.
I
I
Gaidarov
M E
ME
Smith
J
J
Domin
J H
JH
Keen
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism*; D022163:Clathrin-Coated Vesicles / Q000201:enzymology / Q000378:metabolism; D004705:Endocytosis; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D006801:Humans; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D021601:trans-Golgi Network / Q000201:enzymology / Q000378:metabolism
D015703:Antigens, CD; D002966:Clathrin; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D010716:Phosphatidylinositols; D019869:Phosphatidylinositol 3-Kinases