Functional anatomy of phospholipid binding and regulation of phosphoinositide homeostasis by proteins of the sec14 superfamily.
Sec14, the major yeast phosphatidylinositol (PtdIns)/phosphatidylcholine (PtdCho) transfer protein, regulates essential interfaces between lipid metabolism and membrane trafficking from the trans-Golgi network (TGN). How Sec14 does so remains unclear. We report that Sec14 binds PtdIns and PtdCho at distinct (but overlapping) sites, and both PtdIns- and PtdCho-binding activities are essential Sec14 activities. We further show both activities must reside within the same molecule to reconstitute a functional Sec14 and for effective Sec14-mediated regulation of phosphoinositide homeostasis in vivo. This regulation is uncoupled from PtdIns-transfer activity and argues for an interfacial presentation mode for Sec14-mediated potentiation of PtdIns kinases. Such a regulatory role for Sec14 is a primary counter to action of the Kes1 sterol-binding protein that antagonizes PtdIns 4-OH kinase activity in vivo. Collectively, these findings outline functional mechanisms for the Sec14 superfamily and reveal additional layers of complexity for regulating phosphoinositide homeostasis in eukaryotes.
Schaaf
Gabriel
G
Department of Cell and Developmental Biology, School of Medicine, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA.
Ortlund
Eric A
EA
Tyeryar
Kimberly R
KR
Mousley
Carl J
CJ
Ile
Kristina E
KE
Garrett
Teresa A
TA
Ren
Jihui
J
Woolls
Melissa J
MJ
Raetz
Christian R H
CR
Redinbo
Matthew R
MR
Bankaitis
Vytas A
VA
D019870:1-Phosphatidylinositol 4-Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology*; D050356:Lipid Metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010716:Phosphatidylinositols / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011987:Receptors, Steroid; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000098825:Oxysterol Binding Proteins
D019870:1-Phosphatidylinositol 4-Kinase; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D049294:Phospholipid Transfer Proteins; D011987:Receptors, Steroid; D029701:Saccharomyces cerevisiae Proteins; C087901:KES1 protein, S cerevisiae; D000098825:Oxysterol Binding Proteins; C483438:SEC14 protein, S cerevisiae