Cellular Localization, Oligomerization, and Membrane Association of the Hereditary Spastic Paraplegia 3A (SPG3A) Protein Atlastin

Abstract

Hereditary spastic paraplegias comprise a group of clinically heterogeneous syndromes characterized by lower extremity spasticity and weakness, with distal axonal degeneration in the long ascending and descending tracts of the spinal cord. The early onset hereditary spastic paraplegia SPG3A is caused by mutations in the atlastin/human guanylate-binding protein-3 gene (renamed here atlastin-1), which codes for a 64-kDa member of the dynamin/Mx/guanylate-binding protein superfamily of large GTPases. The atlastin-1 protein is localized predominantly in brain, where it is enriched in pyramidal neurons in the cerebral cortex and hippocampus. In cultured cortical neurons, atlastin-1 co-localized most prominently with markers of the Golgi apparatus, and immunogold electron microscopy revealed a predominant localization of atlastin-1 to the cis-Golgi. Yeast two-hybrid analyses and co-immunoprecipitation studies demonstrated that atlastin-1 can self-associate, and gel-exclusion chromatography and chemical cross-linking studies indicated that atlastin-1 exists as an oligomer in vivo, most likely a tetramer. Membrane fractionation and protease protection assays revealed that atlastin-1 is an integral membrane protein with two predicted transmembrane domains; both the N-terminal GTP-binding and C-terminal domains are exposed to the cytoplasm. Together, these findings indicate that the SPG3A protein atlastin-1 is a multimeric integral membrane GTPase that may be involved in Golgi membrane dynamics or vesicle trafficking. Hereditary spastic paraplegias comprise a group of clinically heterogeneous syndromes characterized by lower extremity spasticity and weakness, with distal axonal degeneration in the long ascending and descending tracts of the spinal cord. The early onset hereditary spastic paraplegia SPG3A is caused by mutations in the atlastin/human guanylate-binding protein-3 gene (renamed here atlastin-1), which codes for a 64-kDa member of the dynamin/Mx/guanylate-binding protein superfamily of large GTPases. The atlastin-1 protein is localized predominantly in brain, where it is enriched in pyramidal neurons in the cerebral cortex and hippocampus. In cultured cortical neurons, atlastin-1 co-localized most prominently with markers of the Golgi apparatus, and immunogold electron microscopy revealed a predominant localization of atlastin-1 to the cis-Golgi. Yeast two-hybrid analyses and co-immunoprecipitation studies demonstrated that atlastin-1 can self-associate, and gel-exclusion chromatography and chemical cross-linking studies indicated that atlastin-1 exists as an oligomer in vivo, most likely a tetramer. Membrane fractionation and protease protection assays revealed that atlastin-1 is an integral membrane protein with two predicted transmembrane domains; both the N-terminal GTP-binding and C-terminal domains are exposed to the cytoplasm. Together, these findings indicate that the SPG3A protein atlastin-1 is a multimeric integral membrane GTPase that may be involved in Golgi membrane dynamics or vesicle trafficking. Hereditary spastic paraplegias (HSPs) 1The abbreviations used are: HSPshereditary spastic paraplegiasGBPguanylate-binding proteinHAhemagglutininPBSphosphate-buffered salineNGSnormal goat serumFPLCfast protein liquid chromatographyCBPcalmodulin-binding peptideNIK/HGKNck-interacting kinase/hematopoietic progenitor kinase/germinal center kinase-like kinaseMAPKmitogen-activated protein kinaseSAPK/JNKstress-activated protein kinase/c-Jun N-terminal kinaseGTPγSguanosine 5′-O-(3-thiotriphosphate)DDP1deafness-dystonia-protein-1. are a group of neurological disorders characterized principally by progressive spasticity and weakness of the lower limbs (1.Tallaksen C.M.E. Dürr A. Brice A. Curr. Opin. Neurol. 2001; 14: 457-463Crossref PubMed Scopus (68) Google Scholar, 2.Crosby A.H. Proukakis C. Am. J. Hum. Genet. 2002; 71: 1009-1016Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar, 5.Reid E. J. Med. Genet. 2003; 40: 81-86Crossref PubMed Scopus (137) Google Scholar). They typically exhibit axonal degeneration in the distal portions of long ascending dorsal column fibers and descending corticospinal tracts of the spinal cord, which constitute the longest motor and sensory axons in the central nervous system (6.Schwartz G.A. Liu C.-N. Arch. Neurol. Psychiatry. 1956; 75: 144-162Crossref Scopus (100) Google Scholar). HSPs have historically been classified as “pure” or “uncomplicated” if spastic paraplegia occurs in isolation and “complicated” if other neurological abnormalities are present (7.Harding A.E. Lancet. 1983; 1: 1151-1155Abstract PubMed Scopus (786) Google Scholar). More recently, the identification of new genetic loci for HSPs has permitted a molecular classification of HSPs (2.Crosby A.H. Proukakis C. Am. J. Hum. Genet. 2002; 71: 1009-1016Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar, 5.Reid E. J. Med. Genet. 2003; 40: 81-86Crossref PubMed Scopus (137) Google Scholar). Of the 20 known loci (SPG1–20), 11 are autosomal dominant, six are autosomal recessive, and three are X-linked. Although most HSP patients experience progressive worsening of their symptoms, for some, the disorder does not appear to be progressive (3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar). Thus, although some HSPs are clearly neurodegenerative disorders (e.g. SPG4), others such as SPG1 (due to mutations in the L1 cell adhesion molecule) and SPG3A (due to mutations in the atlastin GTPase) may be neurodevelopmental disorders (3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar). hereditary spastic paraplegias guanylate-binding protein hemagglutinin phosphate-buffered saline normal goat serum fast protein liquid chromatography calmodulin-binding peptide Nck-interacting kinase/hematopoietic progenitor kinase/germinal center kinase-like kinase mitogen-activated protein kinase stress-activated protein kinase/c-Jun N-terminal kinase guanosine 5′-O-(3-thiotriphosphate) deafness-dystonia-protein-1. Eight disease genes for HSPs have now been identified; and based on the proteins involved, several mechanisms for pathogenesis have been advanced. These include aberrant cell signaling or migration, abnormalities of mitochondrial chaperones, abnormalities of myelination, and defects in intracellular trafficking and transport (2.Crosby A.H. Proukakis C. Am. J. Hum. Genet. 2002; 71: 1009-1016Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar, 5.Reid E. J. Med. Genet. 2003; 40: 81-86Crossref PubMed Scopus (137) Google Scholar). Proteins mutated in HSPs that have been implicated in cellular protein or vesicle trafficking include KIF5A (SPG10), spastin (SPG4), spartin (SPG20; Troyer syndrome), and atlastin (SPG3A) (reviewed in Refs. 2.Crosby A.H. Proukakis C. Am. J. Hum. Genet. 2002; 71: 1009-1016Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar, 5.Reid E. J. Med. Genet. 2003; 40: 81-86Crossref PubMed Scopus (137) Google Scholar). KIF5A is a neuronal kinesin heavy chain motor protein involved in the transport of macromolecules and membranous organelles along the axon (8.Reid E. Kloos M. Ashley-Koch A. Hughes L. Bevan S. Svenson I.K. Graham F.L. Gaskell P.C. Dearlove A. Pericak-Vance M.A. Rubinsztein D.C. Marchuk D.A. Am. J. Hum. Genet. 2002; 71: 1189-1194Abstract Full Text Full Text PDF PubMed Scopus (426) Google Scholar). Spastin, a member of the AAA (for ATPases associated with a variety of cellular activities) protein family, associates with microtubules, and spastin overexpression causes microtubule disassembly (9.Errico A. Ballabio A. Rugarli E.I. Hum. Mol. Genet. 2002; 11: 153-163Crossref PubMed Scopus (284) Google Scholar). The spartin protein is similar to the VPS4, SNX15 (sorting nexin-15), and SKD1 proteins, which are involved in endosome morphology and protein trafficking of endosomal compartments (10.Patel H. Cross H. Proukakis C. Hershberger R. Bork P. Ciccarelli F.D. Patton M.A. McKusick V.A. Crosby A.H. Nat. Genet. 2002; 31: 347-348Crossref PubMed Scopus (212) Google Scholar). These latter proteins share with both spastin and spartin a region called the MIT (contained within microtubule-interacting and trafficking molecules) or ESP (present in End13/VPS4, SNX15, and PalB) domain (2.Crosby A.H. Proukakis C. Am. J. Hum. Genet. 2002; 71: 1009-1016Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 11.Ciccarelli F.D. Proukakis C. Patel H. Cross H. Azam S. Patton M.A. Bork P. Crosby A.H. Genomics. 2003; 81: 437-441Crossref PubMed Scopus (122) Google Scholar). Based on its similarity to members of the dynamin/Mx/guanylate-binding protein (GBP) superfamily of large GTPases (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar), the SPG3A protein atlastin (renamed here atlastin-1) has been implicated in intracellular trafficking, yet little is known regarding its cellular localization or function (13.Zhao X. Alvarado D. Rainier S. Lemons R. Hedera P. Weber C.H. Tukel T. Apak M. Heiman-Patterson T. Ming L. Bui M. Fink J.K. Nat. Genet. 2001; 29: 326-331Crossref PubMed Scopus (298) Google Scholar). Among the HSPs, SPG3A is particularly notable for the very early onset of pure spastic paraplegia. Five missense mutations and one single base insertion with premature termination of the predicted 558-amino acid coding region of atlastin-1 have been reported (13.Zhao X. Alvarado D. Rainier S. Lemons R. Hedera P. Weber C.H. Tukel T. Apak M. Heiman-Patterson T. Ming L. Bui M. Fink J.K. Nat. Genet. 2001; 29: 326-331Crossref PubMed Scopus (298) Google Scholar, 14.Muglia M. Magariello A. Nicoletti G. Patitucci A. Gabriele A.L. Conforti F.L. R. M. B. M. G. A. Ann. Neurol. 2002; 51: PubMed Scopus Google Scholar, A. C. M. C. D. C. M. G. G.A. E. 2002; PubMed Scopus Google Scholar, E. A. A. 2003; PubMed Scopus Google Scholar). has been that these mutations may the or GTPase of atlastin-1 (13.Zhao X. Alvarado D. Rainier S. Lemons R. Hedera P. Weber C.H. Tukel T. Apak M. Heiman-Patterson T. Ming L. Bui M. Fink J.K. Nat. Genet. 2001; 29: 326-331Crossref PubMed Scopus (298) Google Scholar, 14.Muglia M. Magariello A. Nicoletti G. Patitucci A. Gabriele A.L. Conforti F.L. R. M. B. M. G. A. Ann. Neurol. 2002; 51: PubMed Scopus Google Scholar, A. C. M. C. D. C. M. G. G.A. E. 2002; PubMed Scopus Google Scholar, E. A. A. 2003; PubMed Scopus Google Scholar). Of the members of the atlastin-1 is most similar to atlastin-1 an of the within the of the guanylate-binding (13.Zhao X. Alvarado D. Rainier S. Lemons R. Hedera P. Weber C.H. Tukel T. Apak M. Heiman-Patterson T. Ming L. Bui M. Fink J.K. Nat. Genet. 2001; 29: 326-331Crossref PubMed Scopus (298) Google Scholar). atlastin-1 a C-terminal and the C-terminal two of of the (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar). that atlastin-1 is an GTPase is of that are integral membrane proteins, with both and exposed to the prominently to the Golgi and is enriched in cerebral cortical pyramidal a of which exhibit a in patients with with J. PubMed Scopus Google Scholar). the domains predicted the system T. S. S. 14: PubMed Scopus Google Scholar). with PubMed Scopus Google Scholar). and coding of the atlastin-1 GTPase by a and by The atlastin-1 the of the with or hemagglutinin the as C. M. 2003; PubMed Scopus Google Scholar). The atlastin-1 the of for of the as a an C-terminal the and as C. M. 2003; PubMed Scopus Google Scholar). and of atlastin-1 with to of C. M. S. A. M. B. G. B. Nat. Genet. 2000; PubMed Scopus Google Scholar, C. G. C. P. L. J. C. E. C. L. B. B. J. Nat. Genet. 2000; PubMed Scopus Google Scholar). and goat have been C. M. 2003; PubMed Scopus Google Scholar). and and in and and for a and a The for a and a The for a and an by the with serum as the and by on or and to with and saline for several with 20 and for several with the by proteins revealed with in by and in for and in phosphate-buffered on a and These in phosphate-buffered saline and in a of and in The the to the in normal goat serum serum and for and for with in serum and In the with the peptide to The with and with in with for with with the for and revealed on and with and of cortical neurons and as J. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). in neurons with for several with and and for in and with atlastin-1 and or in and three with with and in and for by three with with a and with cortical as in neurons with in for and with The and in and for and with or as a in for with in with in with in in for with in the with in for the with and and with and The with in for with in and with of and and in of with and and a electron with an Membrane atlastin-1 with and in and a the The and for a membrane and a The membrane with and with with with and or with and as indicated and for to a and In other and membrane atlastin-1 or atlastin-1 of the and membrane with atlastin-1 and membrane to with as by C. J. Full Text PDF PubMed Google Scholar), and of the and with and atlastin-1 with and in and a and the for The and the for latter in the with or or with by in with the or of atlastin-1 or with with peptide as J. PubMed Scopus Google Scholar). Yeast two-hybrid the the genes and the of as C. M. 2003; PubMed Scopus Google Scholar). by and and by of by and as C. M. 2003; PubMed Scopus Google Scholar). and with and or with with and in and and by for of for with of to protein three with and proteins by and with cross-linking with the in and for on by and with or of atlastin-1 in in and and by for The to a column a of in and and proteins by and and in and to the column to a which the molecular for and of atlastin-1 GTPase atlastin-1 for the of calmodulin-binding peptide proteins of in by for in and and by two a cell The by for and to with and proteins with and protein and The for the GTPase with serum and in of the on by ascending chromatography in and The and and and GTPase as a of to of GTP-binding and protein for proteins similar to atlastin (renamed atlastin-1) and two proteins which as have The other have the atlastin-1 gene is on the gene to and the gene to These proteins with a large central of similarity that the GTP-binding region in the N-terminal the most occurs the and is acid and similarity atlastin-1 and the central and and similarity atlastin-1 and and share and similarity two predicted transmembrane T. S. S. 14: PubMed Scopus Google are in three the and the GTPase predicted transmembrane with (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar). for and reported for atlastin-1 (13.Zhao X. Alvarado D. Rainier S. Lemons R. Hedera P. Weber C.H. Tukel T. Apak M. Heiman-Patterson T. Ming L. Bui M. Fink J.K. Nat. Genet. 2001; 29: 326-331Crossref PubMed Scopus (298) Google are not in and and of the the and of on of with its predicted not in with both the and not in and brain, with protein The the with the peptide not most enriched in brain, present in several other lower the mitochondrial protein a the localization of atlastin-1 by atlastin-1 and the protein enriched in the In the mitochondrial protein most in the with lower in the the localization of atlastin-1 in the of atlastin-1 most in of the cerebral the motor Although the neuronal most the the with the peptide within the in pyramidal neurons in and and the other in the Although little present in the with to a of large neurons, in neurons within the and several and C. of in several the dorsal and the and C. the localization of atlastin-1 the cultured cerebral cortical neurons most prominently in the cell with in neuronal both axons and very with markers for the and of atlastin-1 with with not a for the Golgi apparatus, co-localized with atlastin-1 with atlastin-1 with the Golgi to a not The atlastin-1 by of the with the peptide not in and axons that associated with the Golgi in the neuronal cell the Golgi of the atlastin-1 the localization of atlastin-1 in cultured cortical neurons by immunogold electron microscopy of immunogold the Golgi apparatus, predominantly the and not present in in which the and in or in the an Membrane on the of fractionation and atlastin-1 is an integral membrane or Golgi it with known proteins membrane in to the membrane which been by to proteins and to a of the protein in the the of The integral membrane protein in the membrane membrane to and to atlastin-1 is an integral membrane to the in a similar to the integral membrane protein atlastin-1 the membrane by or both atlastin-1 and by In the of not by by both and with demonstrated a of atlastin-1 predominantly to the the protein in the the two domains in atlastin-1 transmembrane used several and C-terminal atlastin-1 to localization to or membrane atlastin-1 present in the membrane and the and not the membrane a C-terminal that the two predicted transmembrane caused a of the protein to the that these domains are for membrane C-terminal atlastin-1 the predicted transmembrane domains for membrane the transmembrane of the atlastin-1 used atlastin-1 in a protease protection to both and of with although for of the N-terminal domain These indicate that both and are exposed to the of the In the protein in the of protease not with is that of the three for in atlastin-1 and not the of atlastin-1 with peptide In the known J. C. D. P. S. D. Hum. Mol. Genet. 2000; PubMed Scopus Google Scholar, J. 2000; Full Text Full Text PDF PubMed Scopus Google in by peptide Thus, have that these in atlastin-1 are in vivo, with transmembrane an of the protein in vivo, and to atlastin-1 as two-hybrid a of atlastin-1 with to the domains for by or with both and C-terminal not an several and C-terminal domain although and have been demonstrated for other members of the superfamily (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar, B. P. J. Full Text Full Text PDF PubMed Scopus Google Scholar, C. M. H. J. J. Full Text Full Text PDF PubMed Scopus Google Scholar, H. H. E. J. Full Text Full Text PDF PubMed Scopus Google Scholar, P. Nat. 2001; PubMed Scopus Google Scholar). In co-immunoprecipitation with of atlastin-1 in Based on the of chemical cross-linking atlastin-1 most likely to be a with and in to the gel-exclusion that atlastin-1 a of with the the atlastin-1 and it to the of to the for the atlastin-1 oligomer by gel-exclusion a for the atlastin-1 protein in which the transmembrane a similar gel-exclusion which the transmembrane as that the two predicted transmembrane domains are for of a proteins, atlastin-1 GTPase of atlastin-1 protein the of Thus, atlastin-1 not as in studies Liu A. L. G. 2002; PubMed Scopus Google Scholar), as a GTPase in the SPG3A gene a very early onset pure HSP (2.Crosby A.H. Proukakis C. Am. J. Hum. Genet. 2002; 71: 1009-1016Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar, 5.Reid E. J. Med. Genet. 2003; 40: 81-86Crossref PubMed Scopus (137) Google Scholar). In have that the SPG3A gene atlastin-1 is an GTPase of that are integral membrane proteins, with both and exposed to the cytoplasm. have two other members of the atlastin of GTPases that share similarity with atlastin-1 and likely the and These proteins are of similar and have the GTP-binding as as two predicted transmembrane the gene to an within the H. Patton M.A. S. Crosby A.H. Am. J. Hum. Genet. 2001; Full Text Full Text PDF PubMed Scopus Google and may be a gene for The gene is in the of the gene spastin on The transmembrane for atlastin-1 is not of the of large GTPases to which the are most F.D. Proukakis C. Patel H. Cross H. Azam S. Patton M.A. Bork P. Crosby A.H. Genomics. 2003; 81: 437-441Crossref PubMed Scopus (122) Google Scholar, B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar, H. H. E. J. Full Text Full Text PDF PubMed Scopus Google Scholar). although the and share an of in the within the guanylate-binding are several the atlastin and (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar, X. Alvarado D. Rainier S. Lemons R. Hedera P. Weber C.H. Tukel T. Apak M. Heiman-Patterson T. Ming L. Bui M. Fink J.K. Nat. Genet. 2001; 29: 326-331Crossref PubMed Scopus (298) Google Scholar, Liu A. L. G. 2002; PubMed Scopus Google Scholar). have an C-terminal domain that to with (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar). have a C-terminal an for which of the has demonstrated that atlastin-1 and likely and are integral membrane proteins with two transmembrane domains; by are not integral membrane In the are of the large GTPases that the mitochondrial membrane with both and the S. D. E. B. J. 2001; PubMed Scopus Google Scholar, M. D. A. J. 2002; PubMed Google Scholar). the are for mitochondrial atlastin-1 may have in or members of the superfamily (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar, H. H. E. J. Full Text Full Text PDF PubMed Scopus Google Scholar, P. Nat. 2001; PubMed Scopus Google Scholar, G. 2002; PubMed Scopus Google Scholar), atlastin-1 Although that atlastin-1 most likely as a it is not it can with and is the are to as has been for other members of the superfamily (12.Prakash B. Praefcke G.J.K. Renault L. Wittinghofer A. Herrmann C. Nature. 2000; 403: 567-571Crossref PubMed Scopus (256) Google Scholar, P. Nat. 2001; PubMed Scopus Google Scholar, G. 2002; PubMed Scopus Google Scholar). Although the of the atlastin proteins are several have proteins by two-hybrid Liu A. L. G. 2002; PubMed Scopus Google Scholar, E. S. S. M. PubMed Scopus (68) Google Scholar). has been to with which is one of the group center a group of kinase kinase that the in a variety of cell Liu A. L. G. 2002; PubMed Scopus Google Scholar). The with atlastin-1 occurs the domain of of atlastin-1 appear to be for the Liu A. L. G. 2002; PubMed Scopus Google Scholar). has been to with an protein that is predominantly associates with in to E. S. S. M. PubMed Scopus (68) Google Scholar). The C-terminal of the two transmembrane is for several and proteins are for proteins such as and to the Golgi J. Nature. 2002; PubMed Scopus (212) Google Scholar, Curr. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). The of these are mutations in the atlastin-1 gene the atlastin-1 one of the reported atlastin-1 mutations in patients with SPG3A missense the other is a insertion in early termination in the C-terminal domain (13.Zhao X. Alvarado D. Rainier S. Lemons R. Hedera P. Weber C.H. Tukel T. Apak M. Heiman-Patterson T. Ming L. Bui M. Fink J.K. Nat. Genet. 2001; 29: 326-331Crossref PubMed Scopus (298) Google Scholar, 14.Muglia M. Magariello A. Nicoletti G. Patitucci A. Gabriele A.L. Conforti F.L. R. M. B. M. G. A. Ann. Neurol. 2002; 51: PubMed Scopus Google Scholar, A. C. M. C. D. C. M. G. G.A. E. 2002; PubMed Scopus Google Scholar, E. A. A. 2003; PubMed Scopus Google Scholar). missense a in the within the GTP-binding of atlastin-1 and may or GTPase M. Magariello A. Nicoletti G. Patitucci A. Gabriele A.L. Conforti F.L. R. M. B. M. G. A. Ann. Neurol. 2002; 51: PubMed Scopus Google Scholar). Although the other missense mutations the atlastin family, their these mutations are in both and C-terminal that in the in may have or These with membrane cellular GTPase and of atlastin-1 with other The atlastin-1 protein is most in brain, although it is present lower in other and brain, atlastin-1 is prominently enriched in the pyramidal neurons in the cerebral a of which exhibit a distal in patients with These motor neurons to lower motor neurons in the spinal cord, and their in a spastic the of these neurons have the longest axons in the central nervous their in SPG3A patients may a for atlastin-1 function in of motor Based on the localization of atlastin-1 to the Golgi and its similarity to members of the superfamily of atlastin-1 may be for Golgi membrane dynamics or vesicle trafficking. Golgi membrane or vesicle trafficking a distal in motor neurons with long transport along axons has been implicated in a of hereditary long the HSP in the neuronal kinesin (8.Reid E. Kloos M. Ashley-Koch A. Hughes L. Bevan S. Svenson I.K. Graham F.L. Gaskell P.C. Dearlove A. Pericak-Vance M.A. Rubinsztein D.C. Marchuk D.A. Am. J. Hum. Genet. 2002; 71: 1189-1194Abstract Full Text Full Text PDF PubMed Scopus (426) Google and the hereditary in the motor C. J. M. T. S. S. T. M. S. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar), as as in an autosomal of lower motor disease in of C. M. E. D. Nat. Genet. 2003; PubMed Scopus Google Scholar). Although these motor proteins of intracellular is as the early onset of SPG3A and that it may be to abnormalities of neuronal (3.Fink J.K. Ann. Neurol. 2002; 51: 669-672Crossref PubMed Scopus (31) Google Scholar, 4.Fink J.K. Neurol. Clin. 2002; 20: 711-726Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar), it is that of neurons with a that the Golgi apparatus, axonal M. G. J. PubMed Google Scholar). Thus, an Golgi is for axonal M. G. J. PubMed Google Scholar), which may be particularly for long axon of the central nervous mutations of atlastin-1 in patients with SPG3A function may in Golgi or to axonal studies of the of SPG3A mutations on Golgi and function as as axonal transport and may the cellular pathogenesis of the HSP J. and D. for S. and for with electron and C. for with