Targeting of hFis1 to Peroxisomes Is Mediated by Pex19p

Abstract

The processes of peroxisome formation and proliferation are still a matter of debate. We have previously shown that peroxisomes share some components of their division machinery with mitochondria. hFis1, a tail-anchored membrane protein, regulates the membrane fission of both organelles by DLP1/Drp1 recruitment, but nothing is known about the mechanisms of the dual targeting of hFis1. Here we demonstrate for the first time that peroxisomal targeting of hFis1 depends on Pex19p, a peroxisomal membrane protein import factor. hFis1/Pex19p binding was demonstrated by expression and co-immunoprecipitation studies. Using mutated versions of hFis1 an essential binding region for Pex19p was located within the last 26 C-terminal amino acids of hFis1, which are required for proper targeting to both mitochondria and peroxisomes. The basic amino acids in the very C terminus are not essential for Pex19p binding and peroxisomal targeting, but are instead required for mitochondrial targeting. Silencing of Pex19p by small interference RNA reduced the targeting of hFis1 to peroxisomes, but not to mitochondria. In contrast, overexpression of Pex19p alone was not sufficient to shift the targeting of hFis1 to peroxisomes. Our findings indicate that targeting of hFis1 to peroxisomes and mitochondria are independent events and support a direct, Pex19p-dependent targeting of peroxisomal tail-anchored proteins. The processes of peroxisome formation and proliferation are still a matter of debate. We have previously shown that peroxisomes share some components of their division machinery with mitochondria. hFis1, a tail-anchored membrane protein, regulates the membrane fission of both organelles by DLP1/Drp1 recruitment, but nothing is known about the mechanisms of the dual targeting of hFis1. Here we demonstrate for the first time that peroxisomal targeting of hFis1 depends on Pex19p, a peroxisomal membrane protein import factor. hFis1/Pex19p binding was demonstrated by expression and co-immunoprecipitation studies. Using mutated versions of hFis1 an essential binding region for Pex19p was located within the last 26 C-terminal amino acids of hFis1, which are required for proper targeting to both mitochondria and peroxisomes. The basic amino acids in the very C terminus are not essential for Pex19p binding and peroxisomal targeting, but are instead required for mitochondrial targeting. Silencing of Pex19p by small interference RNA reduced the targeting of hFis1 to peroxisomes, but not to mitochondria. In contrast, overexpression of Pex19p alone was not sufficient to shift the targeting of hFis1 to peroxisomes. Our findings indicate that targeting of hFis1 to peroxisomes and mitochondria are independent events and support a direct, Pex19p-dependent targeting of peroxisomal tail-anchored proteins. In recent years it has become apparent that peroxisomes and mitochondria are two organelles having more in common than previously assumed (1Schrader M. Yoon Y. BioEssays. 2007; 29: 1105-1114Crossref PubMed Scopus (106) Google Scholar). Besides their metabolic interplay, for example in fatty acid β-oxidation, lipid homeostasis, and reactive oxygen species metabolism, an overlap in the division machinery of both organelles was also discovered (2Schrader M. Biochim. Biophys. Acta. 2006; 1763: 531-541Crossref PubMed Scopus (116) Google Scholar). The dynamin-like protein DLP1/Drp1 known to participate in mitochondrial fission (3Smirnova E. Griparic L. Shurland D.L. van der Bliek A.M. Mol. Biol. Cell. 2001; 12: 2245-2256Crossref PubMed Scopus (1311) Google Scholar, 4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar) was shown to be involved in peroxisomal division as well (5Koch A. Thiemann M. Grabenbauer M. Yoon Y. McNiven M.A. Schrader M. J. Biol. Chem. 2003; 278: 8597-8605Abstract Full Text Full Text PDF PubMed Scopus (272) Google Scholar, 6Li X. Gould S.J. J. Biol. Chem. 2003; 278: 17012-17020Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar), where it is required for the final scission of the organelles (3Smirnova E. Griparic L. Shurland D.L. van der Bliek A.M. Mol. Biol. Cell. 2001; 12: 2245-2256Crossref PubMed Scopus (1311) Google Scholar, 4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, 7Koch A. Schneider G. Luers G.H. Schrader M. J. Cell Sci. 2004; 117: 3995-4006Crossref PubMed Scopus (122) Google Scholar). A patient with a mutation in DLP1 has recently been described (8Waterham H.R. Koster J. van Roermund C.W. Mooyer P.A. Wanders R.J. Leonard J.V. N. Engl. J. Med. 2007; 356: 1736-1741Crossref PubMed Scopus (578) Google Scholar). The DLP1 mutation results in a lethal disorder whereby fission of both mitochondria and peroxisomes is impaired. These findings further underline the importance of organelle dynamics for health and disease (9Detmer S.A. Chan D.C. Nat. Rev. Mol. Cell. Biol. 2007; 8: 870-879Crossref PubMed Scopus (1013) Google Scholar, 10Herzig S. Martinou J.C. Curr. Mol. Med. 2008; 8: 131-137Crossref PubMed Scopus (56) Google Scholar). Mitochondrial fission is regulated at least partly by hFis1, a 17-kDa tail-anchored (TA) 2The abbreviations used are: TA, tail-anchored; ER, endoplasmic reticulum; GFP, green fluorescent protein; IP, immunoprecipitation; MDV, mitochondria-derived vesicle; Pex, peroxin; PMP, peroxisomal membrane protein; TRITC, tetramethylrhodamine isothiocyanate; YFP, yellow fluorescent protein; HA, hemagglutinin; siRNA, small interference RNA; DSP, dithiobis(succinimidylpropionate); MOPS, 4-morpholinepropanesulfonic acid. 2The abbreviations used are: TA, tail-anchored; ER, endoplasmic reticulum; GFP, green fluorescent protein; IP, immunoprecipitation; MDV, mitochondria-derived vesicle; Pex, peroxin; PMP, peroxisomal membrane protein; TRITC, tetramethylrhodamine isothiocyanate; YFP, yellow fluorescent protein; HA, hemagglutinin; siRNA, small interference RNA; DSP, dithiobis(succinimidylpropionate); MOPS, 4-morpholinepropanesulfonic acid. protein of the mitochondrial outer membrane (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, 11James D.I. Parone P.A. Mattenberger Y. Martinou J.C. J. Biol. Chem. 2003; 278: 36373-36379Abstract Full Text Full Text PDF PubMed Scopus (517) Google Scholar, 12Stojanovski D. Koutsopoulos O.S. Okamoto K. Ryan M.T. J. Cell Sci. 2004; 117: 1201-1210Crossref PubMed Scopus (256) Google Scholar). hFis1, as the yeast homolog Fis1p, possesses a single transmembrane domain located to a C terminus in the of the organelle (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, J. Cell Biol. PubMed Scopus Google Scholar). The domain a M. M. R.J. N. J. Mol. Biol. 2003; PubMed Scopus Google Scholar, S.J. 2004; PubMed Scopus Google Scholar, M. A. N. R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), which is to with DLP1/Drp1 R.J. Yoon Y. J. Cell Sci. PubMed Scopus Google Scholar). We and have recently demonstrated that hFis1 also to the peroxisomal membrane and that it is peroxisomal fission by DLP1/Drp1 to peroxisomes A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar, S. A. Y. Cell 2007; PubMed Scopus Google Scholar). the of hFis1 on peroxisomes and mitochondria has been shown to peroxisomal and mitochondrial division (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). both organelles have to for and hFis1 has a in DLP1 to peroxisomes and mitochondria. A of yeast in peroxisomal division has also been K. S. A.M. K. M. M. van der J. Cell Sci. 2006; PubMed Scopus Google Scholar). hFis1 is of the membrane known to be to both peroxisomes and mitochondria (2Schrader M. Biochim. Biophys. Acta. 2006; 1763: 531-541Crossref PubMed Scopus (116) Google Scholar). it is not dual targeting is tail-anchored protein, has been which is to both peroxisomes and and is to a in organelle as well and van der A. M. Mol. Biol. Scholar). to the of the transmembrane domain to the C a of and have to be their a recent N. S. S. Curr. Cell Biol. 2007; PubMed Scopus Google Scholar). The targeting of for the to and the are in their C the transmembrane domain N. S. S. Curr. Cell Biol. 2007; PubMed Scopus Google Scholar, 2001; PubMed Scopus Google Scholar, N. S. E. J. Cell Biol. 2003; PubMed Scopus Google Scholar). The import of mitochondrial is in the a transmembrane domain with and by basic amino acids N. S. S. Curr. Cell Biol. 2007; PubMed Scopus Google Scholar). the the import of mitochondrial membrane D. 2003; PubMed Scopus Google Scholar, Rev. 2007; PubMed Scopus Google Scholar), is that the targeting of mitochondrial is independent of K. K. J. 2006; PubMed Scopus Google Scholar, S.J. G. D. J. Cell Sci. 2008; PubMed Scopus Google Scholar). on protein targeting to peroxisomes are in Y. L. van S. J. PubMed Scopus Google Scholar, Cell. PubMed Scopus Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, K. K. M. M. M. Cell 2001; PubMed Scopus Google Scholar, A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar), and have very recently been further by the of a mitochondria to peroxisomes M. E. M.A. Curr. Biol. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar). of membrane to peroxisomes be by the by the a E. M. Biochim. Biophys. Acta. 2006; 1763: PubMed Scopus Google Scholar), and mitochondria by a of peroxisomal membrane are to be peroxisomes the Pex19p, a protein that as import for X. Y. Gould S.J. J. Cell Biol. PubMed Scopus Google Scholar, A. S. J. Cell Biol. PubMed Scopus Google Scholar, M. Mol. Cell. Biol. 2001; PubMed Scopus Google Scholar, J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar, A. S. K. Mol. Biol. Cell. 2004; PubMed Scopus Google Scholar, A. S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) and to the peroxisomal membrane by with G. J. Cell Biol. 2003; PubMed Scopus Google Scholar, Y. J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar, Y. Y. M. Biochim. Biophys. Acta. 2006; 1763: PubMed Scopus Google Scholar, Y. Y. J. Cell Sci. 2006; PubMed Scopus Google Scholar). In a recent it has been that the peroxisomal and yeast the machinery for the import of and are by binding of Pex19p A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar). In we have the membrane targeting of hFis1. We that the C-terminal domain of hFis1 a Pex19p binding and that Pex19p is required for peroxisomal targeting of hFis1. Pex19p binding is independent of basic amino acid in the C terminus of hFis1, which are instead required for mitochondrial targeting. We first for a direct, Pex19p-dependent targeting of tail-anchored hFis1 to peroxisomes. and to green fluorescent protein the and the hFis1 and and a the C-terminal 26 amino acids of hFis1 to yellow fluorescent protein described previously (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). hFis1 and to and by M. Ryan D. Koutsopoulos O.S. Okamoto K. Ryan M.T. J. Cell Sci. 2004; 117: 1201-1210Crossref PubMed Scopus (256) Google to the and was a to the was described previously M. J.C. G. D. Gould S.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). was The used to the of by and Using the for and at the of the final was the and and by was by A. of and was a M. Ryan Y. of and also used for as well as and also and used for and used for and to tetramethylrhodamine to and Cell RNA and in as described previously M. S.J. J. Cell Sci. PubMed Google Scholar). the with by with M. J.C. G. D. Gould S.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, D. Y. PubMed Scopus Google Scholar). the with the expression of Pex19p by RNA small RNA was the by A. Schrader M. J. PubMed Scopus Google Scholar). The as and and J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar) with with with the by with for and for peroxisomal import and and on with in with and with and as described M. J.C. G. D. Gould S.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). for an with a with an by on an a for and of peroxisomal and as with in peroxisomes as described previously M. E. Luers G. A. J. Cell Biol. Google Scholar). on by single peroxisomes and the was and two and to independent by of for are as with an used to as and as the of Pex19p and hFis1, with hFis1 and Pex19p not for of in some to by with the as described (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). by a a and by at for by for In of with a with of was The with the for was by of of a of to and with at The with by time with and in which also the The and the on by and by the of hFis1 with peroxisomes, peroxisomal to a X. Gould S.J. J. Biol. Chem. 2003; 278: 17012-17020Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar). in MOPS, by a The was by for and peroxisomes by at for The organelle was in and the peroxisomal by for with by with The with X. Gould S.J. J. Biol. Chem. 2003; 278: 17012-17020Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar), and the by and and by on to a and by and with a and of Pex19p and is a involved in the targeting of peroxisomal membrane J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, Curr. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). it was shown that Pex19p as a targeting for the peroxisomal protein A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar). Pex19p is also involved in peroxisomal targeting of hFis1, we first co-immunoprecipitation studies. with and and and with as well as was to with was to with These results that Pex19p and hFis1 are of the Pex19p binding region is located in the C terminus of hFis1 and not basic amino of with and by with to The of the was by that Pex19p binding to hFis1 is of the C-terminal the transmembrane domain of hFis1 and with and with and as by and The by with that the C-terminal domain of hFis1 26 amino to is sufficient to and that of the basic amino acids in the very C terminus of hFis1 not binding to amino acid of the C terminus acids of hFis1. The transmembrane domain is and basic amino acids and are in of A and are shown in of required the of a with be and was a for we that which was previously shown to Pex19p J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar, A. S. K. Mol. Biol. Cell. 2004; PubMed Scopus Google Scholar), was to also of the of Pex19p with hFis1 was not with to with Pex19p was to with hFis1, and the of Pex19p was These further support an hFis1 and Pex19p to the C of and have recently shown that an C terminus of hFis1 is and sufficient for peroxisomal and mitochondrial targeting (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). of the C-terminal of amino acids proper targeting of hFis1 to peroxisomes and mitochondria. further the of Pex19p and hFis1, of hFis1 used for and The the C-terminal amino acids the last 26 amino which the C-terminal and the transmembrane that both are to peroxisomes to instead a more (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). In with the was reduced by of in to and for a the of amino acids the C terminus of hFis1 the binding of the that Pex19p to the C terminus of hFis1, was used for of the last 26 amino acids of hFis1 transmembrane domain and the to the C terminus of was previously shown that is to peroxisomes and mitochondria A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). of and by a of with both it that the C-terminal of hFis1 with the transmembrane domain is sufficient and to Pex19p and to hFis1 to peroxisomes. to and amino acids to a transmembrane domain shown to be for targeting of N. S. S. Curr. Cell Biol. 2007; PubMed Scopus Google Scholar) as well as for targeting of peroxisomal membrane E. M. Biochim. Biophys. Acta. 2006; 1763: PubMed Scopus Google Scholar). The basic amino acids in the C-terminal of hFis1 are to be of a targeting hFis1 two at and and basic was shown to be for proper mitochondrial targeting of hFis1 D. Koutsopoulos O.S. Okamoto K. Ryan M.T. J. Cell Sci. 2004; 117: 1201-1210Crossref PubMed Scopus (256) Google Scholar). the targeting to peroxisomes also depends on we the targeting and Pex19p binding of hFis1 In of the alone both been mutated to for and the was not to and some to the was D. Koutsopoulos O.S. Okamoto K. Ryan M.T. J. Cell Sci. 2004; 117: 1201-1210Crossref PubMed Scopus (256) Google Scholar). was in it still to peroxisomes The of the peroxisomes in a of with the peroxisomal mitochondrial of was of to the was also to a mitochondrial import D. Koutsopoulos O.S. Okamoto K. Ryan M.T. J. Cell Sci. 2004; 117: 1201-1210Crossref PubMed Scopus (256) Google Scholar). In the single and to peroxisomes not We that the basic within the C-terminal of hFis1 is not for peroxisomal targeting. we the two C-terminal of hFis1 are required for the binding of Pex19p to hFis1. of with to be as as with and for a These findings the and indicate that the basic within the C-terminal of hFis1 is not essential for binding of an of the hFis1 their and their of hFis1 to of we overexpression of Pex19p to a shift in the targeting of hFis1 peroxisomes. peroxisomal in we a which and C the K. S. Y. PubMed Scopus Google Scholar), to peroxisomes In to peroxisomal membrane M. J.C. G. D. Gould S.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), of the peroxisomal by which have the of hFis1 with alone with of the peroxisomes by The organelle was in a to and peroxisomal by X. Gould S.J. J. Biol. Chem. 2003; 278: 17012-17020Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar). The of hFis1 with a very in the of hFis1 with peroxisomal overexpression of Pex19p was as and of mitochondrial and to be in and in very but in and not a shift of the targeting of hFis1 peroxisomes was not by Pex19p, of the peroxisomal import machinery are to be by on further the of Pex19p in the peroxisomal targeting of hFis1, RNA interference was previously shown that the of Pex19p with the import of J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar) peroxisomes. of Pex19p to of to mitochondria A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar). of with in a in the protein of Pex19p also by A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar, J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar), peroxisomes still and the of peroxisomal membrane and A. S. K. J. Cell Sci. 2006; PubMed Scopus Google not of Pex19p the peroxisomal targeting of hFis1. Pex19p in was by with the with and the targeting of to peroxisomes was with to and of and peroxisomes in and in for Pex19p are shown on the in of the of of with of Pex19p of and on by single peroxisomes, and the peroxisomes in as well as are as and are independent the of the Pex19p on peroxisome expression of was The expression of in a proliferation of peroxisomes, which of the peroxisomal by division small peroxisomes M. J.C. G. D. Gould S.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, X. Gould S.J. J. Cell Biol. PubMed Scopus (116) Google Scholar). the is to and to by In it was shown that yeast and to Pex19p J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar, A. S. K. Mol. Biol. Cell. 2004; PubMed Scopus Google Scholar) We the of Pex19p have an on the of peroxisomal and on peroxisome of Pex19p, with by and for of Pex19p, the of peroxisomes in was reduced and with A and with a of These findings indicate that of Pex19p is in not but the targeting of to peroxisomes. of hFis1 to but to on the of Pex19p on targeting of hFis1 to peroxisomes. of Pex19p with by The for of and for import of peroxisomes by with In to the of that with peroxisomes by was peroxisomes a very for not at In the of the peroxisomes for A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). These time to the that of Pex19p not import of In a the of peroxisomal and was and the In with the the was reduced of Pex19p with These demonstrate that targeting of hFis1 to peroxisomes A of hFis1 to organelles to the as for and A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar, J.C. Gould S.J. J. Cell Biol. 2004; PubMed Scopus Google Scholar) not the the of Pex19p not the mitochondrial targeting of hFis1. in with the mitochondrial and mitochondria to the as a of expression and A of hFis1 targeting to mitochondria Pex19p was not by by of The of the peroxisomal import of hFis1 of Pex19p further the that Pex19p as a for hFis1 targeting to peroxisomes. Our on the dual targeting of the protein hFis1 to peroxisomes and mitochondria that hFis1 the targeting Our findings further support the recent that in to and mitochondrial outer peroxisomal of a which is by peroxisomal membrane N. S. S. Curr. Cell Biol. 2007; PubMed Scopus Google Scholar, A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar). In a recent for Pex19p have been in the C-terminal of the peroxisomal and yeast A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar). The of hFis1 C-terminal 26 amino acids the transmembrane domain and the acid is with the that targeting for are located at the C and the single transmembrane the of hFis1 is very contrast, that of amino acids A. S. K. J. Cell Sci. 2006; PubMed Scopus Google The C-terminal acids of hFis1 are required for both peroxisomal and mitochondrial targeting, and are sufficient to an protein to both organelles A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). We that the C-terminal 26 amino acids of hFis1 have of the C-terminal 26 amino acids the acid Pex19p binding as well as peroxisomal targeting. In a protein the C-terminal 26 amino acids was to with These demonstrate that the C terminus of hFis1 is sufficient and for Pex19p binding and targeting to peroxisomes. In with a Pex19p binding in the transmembrane region of hFis1 acids was also by a recently A. S. K. Mol. Biol. Cell. 2004; PubMed Scopus Google Scholar, A. S. E. J. G. Wanders R.J. A. 2007; PubMed Scopus Google Scholar). In two binding have been in the of hFis1. of the transmembrane domain the last C-terminal amino acids of hFis1 reduced the with that the Pex19p binding within the transmembrane domain is the essential In the binding are of binding Pex19p, and in targeting A for Pex19p in peroxisomal targeting of hFis1 is further by Silencing of Pex19p was shown to the targeting of hFis1 to peroxisomes, but not to mitochondria. The import of mitochondrial is to be a transmembrane domain with and by basic amino acids N. S. S. Curr. Cell Biol. 2007; PubMed Scopus Google Scholar). hFis1 two at and which are required for proper mitochondrial targeting D. Koutsopoulos O.S. Okamoto K. Ryan M.T. J. Cell Sci. 2004; 117: 1201-1210Crossref PubMed Scopus (256) Google Scholar). of the alone both to not peroxisomal targeting of hFis1. with binding to Pex19p was also not These findings indicate that the basic within the C-terminal of hFis1 is not essential for binding of Pex19p and targeting to peroxisomes. In contrast, both are for mitochondrial targeting. In to peroxisomal which to the machinery for the import of peroxisomal membrane protein import the mitochondrial outer membrane was recently shown to be independent of the import the and also K. K. J. 2006; PubMed Scopus Google Scholar, S.J. G. D. J. Cell Sci. 2008; PubMed Scopus Google Scholar). it is not an to mitochondrial proteins. to with for to the mitochondrial the of a in targeting K. K. J. 2006; PubMed Scopus Google Scholar). a of the lipid of the mitochondrial outer membrane in the of has been recently S.J. G. D. J. Cell Sci. 2008; PubMed Scopus Google Scholar). hFis1 is to be a in the of peroxisomal as well as mitochondrial fission by of DLP1/Drp1 (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). as and fission are for organelle and of the components involved has been to disease (8Waterham H.R. Koster J. van Roermund C.W. Mooyer P.A. Wanders R.J. Leonard J.V. N. Engl. J. Med. 2007; 356: 1736-1741Crossref PubMed Scopus (578) Google Scholar, S.A. Chan D.C. Nat. Rev. Mol. Cell. Biol. 2007; 8: 870-879Crossref PubMed Scopus (1013) Google Scholar, 10Herzig S. Martinou J.C. Curr. Mol. Med. 2008; 8: 131-137Crossref PubMed Scopus (56) Google Scholar). in the of hFis1 at the organelle has been shown to mitochondrial as well as peroxisomal division (4Yoon Y. Krueger E.W. Oswald B.J. McNiven M.A. Mol. Cell. Biol. 2003; 23: 5409-5420Crossref PubMed Scopus (629) Google Scholar, A. Yoon Y. McNiven M.A. Schrader M. Mol. Biol. Cell. PubMed Scopus Google Scholar). both organelles have to for of hFis1 of peroxisome proliferation mitochondrial is very that hFis1 to both peroxisomes and mitochondria at the organelle is regulated and Pex19p to hFis1 of the to peroxisomes and the of The of hFis1 is and the mitochondrial membrane S.J. G. D. J. Cell Sci. 2008; PubMed Scopus Google Scholar), the of a import is to which is to peroxisomes in a Pex19p-dependent peroxisomes are Pex19p is not is to mitochondria. a is involved in the mitochondrial targeting of hFis1, it with Pex19p for hFis1 a is not it to be hFis1 is not to peroxisomes of peroxisome has to be targeting is regulated by the of hFis1 Pex19p in the of Pex19p on hFis1 targeting to peroxisomes. We that of the peroxisomal import machinery are be the peroxisomal membrane for Pex19p Y. Y. M. Biochim. Biophys. Acta. 2006; 1763: PubMed Scopus Google Scholar). for the peroxisomal membrane also to be to the and to peroxisomes by targeting Y. L. van S. J. PubMed Scopus Google Scholar, Cell. PubMed Scopus Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, K. K. M. M. M. Cell 2001; PubMed Scopus Google Scholar). We that hFis1 is to peroxisomes by binding to Pex19p, and that it not the to peroxisomes. targeting, which is to by in the of a mitochondrial targeting was the in the C-terminal of hFis1. on the targeting of to peroxisomes have been further by the of a mitochondria to peroxisomes, which M. E. M.A. Curr. Biol. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar). for hFis1 targeting to peroxisomes be mitochondria by a of the by M. E. M.A. Curr. Biol. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar) are more for a peroxisomal targeting of hFis1. a of is to a small of peroxisomes, hFis1 is in to peroxisomes. hFis1 has not been to be a of We that targeting of hFis1 to peroxisomes and mitochondria are independent on protein targeting to peroxisomes is still to the small of and Cell. PubMed Scopus Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar). Besides hFis1, which has been the first protein discovered to to both mitochondria and peroxisomes, a protein, has very recently been discovered and van der A. M. Mol. Biol. Scholar). hFis1, is also to be involved in mitochondrial and peroxisomal but to be in yeast and van der A. M. Mol. Biol. Scholar). The known peroxisomal in the yeast are and K. S. A.M. K. M. M. van der J. Cell Sci. 2006; PubMed Scopus Google Scholar, A. S. K. J. Cell Sci. 2006; PubMed Scopus Google Scholar). Using a for Pex19p binding A. S. K. Mol. Biol. Cell. 2004; PubMed Scopus Google Scholar, A. S. E. J. G. Wanders R.J. A. 2007; PubMed Scopus Google Scholar), a Pex19p binding acids also be in is of binding Pex19p has to be and findings support a direct, Pex19p-dependent targeting of peroxisomal proteins. We and with