FYVE-finger proteins--effectors of an inositol lipid

Harald Stenmark 1 Rein Aasland 0 0 Dept of Molecular Biology, University of Bergen , N-5020 Bergen, Norway 1 Dept of Biochemistry, the Norwegian Radium Hospital , Montebello, N-0310 Oslo, Norway FYVE-finger proteins - effectors of an inositol lipid SUMMARY The binding of cytosolic proteins to specific intracellular membranes containing phosphorylated derivatives of phosphatidylinositol (PtdIns) is a common theme in vital cellular processes, such as cytoskeletal function, receptor signalling and membrane trafficking. Recently, several potential effectors of the phosphoinositide 3-kinase product PtdIns 3-phosphate (PtdIns(3)P) have emerged through the observation that a conserved zinc-finger-like domain, the FYVE-finger, binds specifically to this lipid. Here we review Many biochemical processes in the cell occur at the interface between the cytosol and an intracellular membrane. Vesicular trafficking, signal transduction and actin-regulated membrane rearrangements are examples of processes that require the recruitment of cytosolic proteins to a specific membrane in a reversible and regulated manner. Such a recruitment is in part accomplished through the binding of cytosolic proteins to the cytoplasmic domains of transmembrane proteins or to the GTP-bound forms of membrane-associated small GTPases. However, an additional mechanism is becoming increasingly evident: many proteins become reversibly localised to membranes through interaction with specific lipid headgroups. Phosphoinositides (PIs), derivatives of phosphatidylinositol (PtdIns) that are phosphorylated at the 3-, 4- or 5-positions of the inositol headgroup, play a central role in this context. The differentially phosphorylated PdtIns headgroups are recognised by specific subsets of cytosolic effector proteins. For instance, many proteins containing pleckstrin homology (PH) domains bind to the abundant phosphoinositide, PtdIns 4,5-bisphosphate (PtdIns(4,5)P2), whereas other PH domain proteins can associate with the rarer PtdIns 3,4,5-trisphosphate (PtdIns(3,4,5)P3) lipid, which is produced by agonist-activated phosphoinositide 3-kinases (PI 3-kinases) (Rameh and Cantley, 1999). Another minor PI 3-kinase product, PtdIns 3-phosphate (PtdIns(3)P), regulates membrane trafficking in yeast and higher eukaryotes, but until recently its protein effectors were not known. Here, we discuss the function of proteins containing a novel zinc finger termed the FYVE-finger, which was recently found to bind specifically to PtdIns(3)P. current knowledge about the structural basis for the FYVE-PtdIns(3)P interaction, its role in membrane recruitment of proteins and the functions of FYVE-finger proteins in membrane trafficking and other cellular processes. THE FYVE-FINGER A CONSERVED PTDINS(3)PBINDING DOMAIN A cysteine-rich domain reminiscent of a zinc finger is involved in the membrane localisation of the autoantigen EEA1, and this motif is present in several other proteins. We dubbed it the FYVE-finger for Fab1p, YOTB, Vac1p and EEA1 (Stenmark et al., 1996). The FYVE finger has eight conserved cysteines, which coordinate two Zn2+ ions in a cross-braced topology (Schwabe and Klug, 1994; Stenmark et al., 1996). In addition, it contains several other conserved residues, most prominently an R(R/K)HHCRxCG motif surrounding the third and fourth cysteine residues (positions 33-41 in Fig. 1). Several hydrophobic positions are also conserved among the FYVE fingers, as is an arginine residue at position 74. Some FYVEfinger proteins deviate from this consensus at a few positions. Recently, the biochemical function of the FYVE finger was revealed when three groups demonstrated that several FYVEfinger proteins bind specifically to PtdIns(3)P (Burd and Emr, 1998; Gaullier et al., 1998; Patki et al., 1998). The highly conserved features of the FYVE fingers strongly suggest that they have very similar structures and that they all bind to PtdIns(3)P or a similar ligand. Several proteins, such as Rabphilin-3A and Rim (see Fig. 1, lower part), have FYVE-related domains that lack several of the conserved features of FYVE fingers, most notably the basic R(R/K)HHCR motif and the arginine residue at position 74. Furthermore, they contain a conserved glycine residue at position 53 instead of that at position 41. The lack of the basic patch indicates that these domains do not bind to PtdIns(3)P, and we have experimentally verified this in the case of Vps27p structure FYVE consensus w# d - C% C F@%% r+hhCr CG ##C cs % % %r#C C# # HsEEA1 lnrkwaednevqncma--cgkg-fsvt----vrrhhcrqcgnifca----ecsaknalt-------psskkpvrvcdacfndlq [1345-1410] CeT10G3.5 ssrkwlddaeaincte--cgkv-fslt----vrkhhcrvcgkiycn----pcssksvri-------asaknpvracntcftdsq [1098-1163] Hs-ae54a12 qghawlkddeathcrq--ceke-fsis----rrkhhcrncghifcn----tcssnelal-------psypkpvrvcdschtlll est Hs-zd64b11 qglvwlkdkeathckl--ceke-fsls----krkhhcrncgeifcn----acsdnelpl-------psspkpvrvcdschalli est ScYGL023p tkdhwipdskrnscry--chkp-ftlw----erkhhcrhcgdifcq----dhlrhwlyl<14>ggingggtlckicddclveye [ 445- 527] ScVps27p tpadwi---dsdacmi--cskk-fsll----nrkhhcrscggvfcq----ehssnsipl-----pdlgiyepvrvcdscfedyd [ 166- 230] Hs-zt93d07_A apaywrpnsqilscnk--cats-fkdn----dtkhhcracgegfcd----scssktrpv----pervwgpapvrvcdncyearn est Hs-zt93d07_B rpaywvpdheilhchn--crke-fsik----lskhhcracgqgfcd----ecshdrrav-----psrgwdhpvrvcfncnkkpg est CeC07G1.5 vapewa---dgpecyr--crsv-fsvf----trkhhcracgqifcd----kcssrelal-----pqfgiekevrvcetcyekkv [ 189- 253] HsHRS rapdwv---daeechr--crvq-fgvm----trkhhcracgqifcg----kcsskysti-----pkfgiekevrvcepcyeqln [ 156- 220] CeT23B5.2 radhwvqdvtrqrcdd--cehk-ftla----drkhhcrncgqifcs----tcsrfeshi-----trmnisrpvrvcrkcfqrlq [ 856- 923] HsKIAA0993 aadhwvkdeggdscsg--csvr-fslt----errhhcrncgqlfcq----kcsrfqsei-----krlkisspvrvcqncyynlq [ 285- 352] Hs-ym48d08 eepqwvpdkecrrcmq--cdak-fdfl----trkhhcrrcgkcfcd----rccsqkvpl-----rrmcfvdpvrqcaecalvsl est HsL33C6p dppewvpdeacgfcta--ckap-ftvi----rrkhhcrscgkifcs----rcsshsapl-----prygqvkpvrvcthcymfhv <8580-9497> CeF22G12.4 aeprws---dgdtcd---cgar-fslt----srkhhcrhcgrhvcs----kcsettmpi-----akygeekrvrvcdvcahvis [1037 1100] MmAnkhzn keppwc---dgsncye--ctak-fgvt----trkhhcrhcgrllch----kcstkeipi-----ikfdlnkpvrvcnicfdvlt [1115-1179] CeF01F1.6 qevrwqwdddvdqcsn--cdts-farv----kvkphclhcgrifcm----nclkdtvps-------gpnhrpanvckvchtlln [ 337- 402] ScPib1p nlarwqadeeahscfq--cktn-fsfl----vrrhhcrccgrifcs----sctenfvny<10>knsdvesppyrtcnecydnll [ 10- 88] HsKIAA0647 evtrwvpdhmashcyn--cdce-fwla----krrhhcrncgnvfca----gcchlklpi-----pdqqlydpvlvcnscyehiq [ 928- 995] HsKIAA0371 emtrwlpdhlaahcya--cdsa-fwla----srkhhcrncgnvfcs----sccnqkvpv-----psqqlfepsrvckscysslh [1112-1179] ScVac1p_A tvtpwrddrsvlfcni--csep-fgll----lrkhhcrlcgmvvcddanrncsneisig<17>ddllhipisirlcshcidmlf [ 208- 297] CeYLN2 etpewk---tsdccqk--cnqpffwnl<10>lrqhhcrtcgsavcg----sccdnwtty-----ppmgyetkiricndcnarmk [ 282- 357] Hs-ys04h11 ktpewl---dsdscqk--cdqpffwnf <10>lrqhhcrkcgkavcg----kcsskrssn-----ppmgfefevrvcdschegit est CeYW91 pnttwe--gesghcay--ckke-fnkls<4>drqhhcrnc (...truncated)