Transport of Lysosome-Related Organelles
Jordens, IngridCitation
Jordens, I. (2005, November 23). Transport of Lysosome-Related Organelles. Retrieved from https://hdl.handle.net/1887/4341
Version: Corrected Publisher’s Version
License: Licence agreement concerning inclusion of doctoral thesis in theInstitutional Repository of the University of Leiden Downloaded from: https://hdl.handle.net/1887/4341
Summary and Di
scussi
on
M ajor histocompatibility complex (M HC) class II molecules are crucialin protecting our body againstpathogens.They are synthesized in the endoplasmatic reticulum (ER) where they form a trimer with the invariant chain (Ii). This complex is transported via the Golgi to the M HC class II containing compartment (M IIC), a specialized compartment where peptide loading occurs.After internalisation,antigens are degraded into peptides during their transport through the endosomal pathway. W hen they arrive in the specialised M IIC, they are loaded onto the M HC class II molecules, a process facilitated by the chaperone HLA-DM . M HC class II-peptide complexes are then transported to the plasma membrane where the antigenic peptide can be recognised by CD4+ T cells [1].
This thesis mainly focused on the transport of M IIC, and other lysosome-related organelles. M HC class II transport towards the plasma membrane is tightly regulated and depends on both the celltype and the activation state of the cells.In M elJuso cells,which are not professional antigen presenting cells (APCs), but have all the requirements for efficient antigen presentation, M IICs are transported to and fuse with the plasma membrane [2,3]. In dendritic cells a different process is observed. Upon activation, M IICs start to form tubular structures, extending into the direction of the contact site with the T cell. However, under these conditions many non-tubulated vesicles existas well[4-6].Both ways of transporthave one thing in common,they require microtubules.
In Chapter 2, we studied the transport of GFP-tagged M HC class II in M el Juso cells. Realtime imaging showed thatmostof the M IIC accumulated in the perinuclear area,where little movement is observed. A small portion of the M IICs is found in the periphery where they move in a peculiar stop-and-go fashion, rapidly changing direction. W e identified the mediators of this transport,which are the plus-end directed motor,kinesin,and the minus-end directed motor complex,dynein-dynactin.Both motors acton the same M IIC,which explains their bi-directionality. Dynein activity usually overrules kinesin, retaining the M IIC in the perinuclear area around the minus-end of the microtubules close to the microtubule organizing centre (M TOC). W hen kinesin activity overrides dynein activity, M IICs are transported into the periphery. Yet the M IIC is not directly transported to the plasma membrane and alters its direction frequently.This suggests thatduring this transportthe two motor activities are regulated, possibly to prevent ‘immature’ M IIC to reach the plasma membrane.
M ultiple highly processive kinesin motor protein variants have been identified with differences in cargo specificity [7,8].Two kinesin motors have been described to be involved in the transport of late endosomal and lysosomal compartments, Kinesin-I and –II [9-11]. Kinesin activity is atleastpartially regulated by phosphorylation,which leads to an increase in its membrane association and a higher processivity of the motor [12-15]. M oreover, recently it was found that Kinesin-II interacts with the p150Glued subunit of dynactin via the kinesin-associated protein (KAP) [16], implying that bi-directional movement may be controlled by one protein complex containing both motor proteins.
Chapter 7
never torn apart by two oppositely directed motor activities [23], there must be a regulator that coordinates the activity of both dynein and kinesin.
Small GTPases are ideal regulators. They are able to switch between an active and an inactive state and have a high compartment specificity, which enables them to act locally. In Chapter 3 we investigated the role of the small GTPase Rab7 in the transport of late endosomal/lysosomal compartments. Rab7 is present on late endosomal/lysosomal compartments, including MIIC, and is known to regulate their transport [18,24-26]. Via a Yeast Two-Hybrid screen with Rab7 as bait, we identified an at that time unidentified protein: Rab7 interacting lysosomal protein (RILP) [27,28]. RILP interacts with the active membrane-bound Rab7 and locks Rab7 in the active GTP-membrane-bound state. Effector proteins like RILP often interact with the GTP-bound state and prolong the active state of their target GTPase. How the interaction between effector and its GTPase is terminated is largely unclear. It might be competition with GTPase activating proteins (GAPs) or other interacting factors that change the conformation of the GTPase. In the case of Rab7, no GAPs or Guanine Exchange Factors (GEFs) have been reported yet.
Besides locking Rab7 in the active state, RILP also induces the recruitment of the minus-end motor complex, dynein-dynactin, onto the late minus-endosomes and lysosomes (Chapter 3). Although for other Rabs and their effectors direct interactions with motor proteins have been shown (Introduction), we were unable to show a direct interaction between either Rab7 or RILP with any component of the dynein/dynactin motor complex. We used immuno-electron microscopy to show that on the lysosomes the dynactin subunit p50dynamitin was mostly found in close proximity of RILP. This indicates that there might be an interaction, although possibly via other proteins. A likely intermediate is E3 spectrin, which is present on late endosomes and lysosomes (our unpublished results) and has been shown to interact with the ARP1 subunit of dynactin [29]. Moreover, via RNAi we showed that spectrin E3 is required for late endosomal/lysosomal retention in the perinuclear area (unpublished results), presumably via its interaction with dynein-dynactin. Spectrin E3 has been shown to bind specifically to acidic phospholipids [30], thus it might be that RILP regulates the lipid content of late endosomal/lysosomal membranes and thereby stimulates dynein-dynactin recruitment via rearrangements in the spectrin network. Interestingly, Zerial and co-workers recently identified a new kinesin member, KIF16B, which has a lipid binding domain. They showed that an effector of Rab5, the PI3 kinase Vps34, locally produces PI(3)P, which results in the recruitment of KIF16B to the endosome [31]. Thus altering the lipid composition of compartments might be a general way to manipulate motor protein recruitment.
Interestingly, not all late endosomes and lysosomes (including MIIC) fuse with the plasma membrane upon arrival in the cell extremities. Especially in the case of MIIC, we could not detect changes in cell surface MHC class II molecules when minus-end transport was abrogated (unpublished results). Apparently, another regulatory step occurs close to the plasma membrane. For several lysosome-related organelles (LRO), including melanosomes and cytolytic granules, it has been shown that actin-based transport is required next to microtubule-based transport [32]. Again various Rab proteins are involved in this actin-based transport, including Rab27a, Rab3 and Rab8 [32,33].
An illustrative example of the cooperation between actin-based and microtubule-based motors is found in melanosomes. Melanosomes are lysosome-related organelles and like lysosomes they move along microtubules in a bi-directional way via the alternating action of kinesin and dynein. In the periphery, melanosomes are captured in the peripheral actin via the small GTPase Rab27a and its effector protein Melanophilin/Slac2a [34-38]. Melanophilin interact with the actin motor Myosin Va and this tripartite structure has been shown to link melanosomes to peripheral actin prior to their transfer to the surrounding keratinocytes.
Since melanosomes are related to lysosomes, we reasoned that Rab7 could also be involved in the transport of melanosomes. Moreover, it has been shown that delivery of TRP-1, which is involved in melanosomal biogenesis, to the melanosomes is Rab7-dependent [39,40]. In chapter 6, we show that Rab7 is mainly present on early stage melanosomes, whereas Rab27a is present on more mature melanosomes. Their distribution overlapped on the intermediate stage melanosomes, which suggests maturation dependent activity of different Rab proteins. We showed that Rab7 and RILP are able to target a major part of the melanosomes to the MTOC. In addition, when both Rab7 and Rab27a are overexpressed we observed that many Rab7-positive compartments moved to the MTOC upon co-expression of RILP. The majority of the Rab7-positive compartments remaining in the periphery contained Rab27a as well. This suggests that there is a competition between Rab7 and Rab27a and their associated motors, dynein and myosin Va respectively.
Fluorescent Recovery after Photo bleaching (FRAP) enabled us to measure the local activities of both Rab7 and Rab27a. Interestingly, the amount of Rab27a in the GTP-bound active state was extremely high in the tips of the melanocytes and less in the perinuclear area. The Rab7 activity did not show these extreme differences. This might explain why Rab27a overrules Rab7 in the periphery and therefore melanosomes in the periphery containing both Rab27a and Rab7 remain associated to the actin via Melanophilin/Myosin Va.
Thus Rab7 keeps melanosomes in the perinuclear area during their early stages of maturation via the action of RILP and dynein. This might be required to keep the immature melanosomes close the Golgi in order to receive biogenetically-related proteins, like Trp1. As the melanosomes mature, they acquire Rab27a and ultimately are captured in the peripheral actin via the action of Rab27a effector Melanophilin/Slac2a and Myosin Va.
Chapter 7
Moreover, Fukuda has shown that several other effectors are shared among Rab3, Rab8 and Rab27a [44], again indicating a possible interplay between different Rabs in one pathway.
Other lysosomal-related organelles that depend on Rab7 are phagosomes. Phagosomes are formed after the internalisation of pathogens by interaction with the endosomal system. By the sequential recruitment of endosomal proteins, phagosomes mature into phagolysosomes [45]. Normally, pathogens are killed and degraded in the phagolysosome. However, some pathogens, like Salmonella, M. Tuberculosis and M. Leprae, can actively inhibit fusion with proteolytic lysosomes. Hence, they create their own intracellular environment in which they are able to survive and replicate [46].
Rab7 is required for the intracellular survival of Salmonella and phagosomes also require the action of kinesin and dynein for microtubule-based transport [47,48]. In Chapter 5 we described the involvement of the Rab7/RILP pathway in intracellular survival of Salmonella. Upon ectopic expression of RILP in cells infected with Salmonella, dynein-dynactin motors were massively recruited onto the Salmonella-containing vacuole (SCV). In addition, we observed an increase in fusion of SCV with mature lysosomes. Most likely, dynein facilitates the targeting of phagosomes towards the mature lysosomes. Moreover, RILP locks Rab7 in the active GTP-bound conformation which may also stimulate fusion with lysosomes. As result, the intracellular survival of Salmonella was dramatically reduced (Chapter 5). Thus by modulating the Rab7/RILP/dynein pathway, the intracellular survival of intracellularly growing pathogens, like Salmonella, was influenced. Interestingly, Salmonella has been shown to actively secret certain factors, like SifA, SopD, and SopE [49,50]. SopE is identified as a GEF for CDC42, involved in the actin rearrangements during uptake [51]. An obvious question would be whether any of the secreted factors interfere with the host cell Rab7 pathway to block downstream events involved in the fusion with mature lysosomes. Recently, SifA has been shown to block RILP recruitment to the SCV and modulates the ‘normal’ fusion with lysosomes [52]. Most likely, other pathogen factors will target this pathway as well.
The exact role of RILP in the lysosomal pathway is not completely clear yet. However, some additional information was obtained from the isolation of a splice variant of RILP, RILPsv (Chapter 4). RILPsv lacks aa 315-342 (Exon VII), yet still contains the Rab7 interaction domain [53,54]. Like full-length RILP, RILPsv is able to lock Rab7 in the active conformation. However, one striking difference is observed, RILPsv fails to recruit the dynein-dynactin complex to late endocytic structures. As a result, upon overexpression of RILPsv, lysosomes do not cluster around the MTOC but smaller separated clusters were formed. The relative localisation to the Golgi nicely illustrates the difference between RILP and RILPsv. The lysosomal cluster in RILP expressing cells is located directly around the MTOC in between the Golgi, whereas the clusters in RILPsv expressing cells were localized outside the Golgi area further away from the MTOC. This implies that beside the N-terminal portion of RILP, also Exon VII is required for the RILP-mediated dynein-dynactin recruitment.
homology (CLH) domain, which is sufficient for homo-oligomerisation and is required for induction of late endosomal/lysosomal clustering. mVps18p and hVam6p are mammalian homologues of proteins of the vacuolar homotypic fusion complex (HOPS) in yeast. They act in the tethering process preceding the actual fusion between late endocytic structures [58-61]. Interestingly, RILP-'N contains the Rab7-binding domain as well as the required for dimerisation, but no lysosomal clustering is observed. This suggests that the N-terminus probably interacts with other proteins involved in clustering of lysosomal compartments. Preliminary data suggest that these proteins are members of the HOPS complex.
As already suggested above, Rab7 is most likely part of a complex of proteins involved in the transport and fusion of late endosomes and lysosomes, similar to the multi-protein Rab5 complex on early endosomes [62]. This complex will include GEFs, effectors, SNAREs, tethering factors, and GAPs. Several Rab7-binding proteins have been isolated, such as the PI3-kinase Vps34 [63] and two Rab7 effectors are identified thus far, RILP and Rabring7 [27,28,64]. Rabring7, like RILP, induces the clustering of Rab7-positive compartments. Rabring7 has a Zinc-finger motive, which is known to be involved in protein-protein interactions [64]. RILP as described above, couples fusion to transport of late endosomes and lysosomes, which will make the fusion process significantly more efficient.
Although the motor is not yet identified, it has been suggested that Rab5 activity besides the plus-end motor KIF16B, is also linked to a minus-end directed motor activity [65]. Since many Rab proteins have been shown to link to motor proteins (Introduction), this may become a common feature of the Rab GTPases to enhance delivery of cargo to their targets by controlling both transport through motor proteins and the fusion machinery.
Concl
usion
Chapter 7
References
1. Wubbolts R, Neefjes J: Intracellular transport and peptide loading of M HC class II molecules: regulation by chaperones and motors.Immunol Rev 1999, 172: 189-208.
2. Wubbolts RW, Fernandez-Borja M, Oomen L, Verwoerd D, Janssen H, Calafat J et al.: Direct vesicular transport of M HC class II molecules from lysosomal structures to the cell surface.J Cell Biol 1996, 135: 611-622.
3. Raposo G, Nijman HW, Stoorvogel W, Liejendekker R, Harding CV, Melief CJ et al.: B lymphocytes secrete antigen-presenting vesicles.J Exp Med 1996, 183: 1161-1172.
4. Boes M, Cerny J, Massol R, Op dB, Kirchhausen T, Chen J et al.: T-cell engagement of dendritic cells rapidly rearranges M HC class II transport.Nature 2002, 418: 983-988.
5. Chow A, Toomre D, Garrett W, Mellman I: Dendritic cell maturation triggers retrograde M HC class II transport from lysosomes to the plasma membrane.Nature 2002, 418: 988-994.
6. Kleijmeer M, Ramm G, Schuurhuis D, Griffith J, Rescigno M, Ricciardi-Castagnoli P et al.: Reorganization of multivesicular bodies regulates M HC class II antigen presentation by dendritic cells.J Cell Biol 2001, 155: 53-63.
7. Goldstein LS: M olecular motors: from one motor many tails to one motor many tales.Trends Cell Biol 2001, 11: 477-482.
8. Hirokawa N: Kinesin and dynein superfamily proteins and the mechanism of organelle transport. Science 1998, 279: 519-526.
9. Bananis E, Nath S, Gordon K, Satir P, Stockert RJ, Murray JW et al.: M icrotubule-dependent movement of late endocytic vesicles in vitro: requirements for Dynein and Kinesin.Mol Biol Cell 2004, 15: 3688-3697.
10. Wubbolts R, Fernandez-Borja M, Jordens I, Reits E, Dusseljee S, Echeverri C et al.: Opposing motor activities of dynein and kinesin determine retention and transport of M HC class II-containing compartments.J Cell Sci 1999, 112 ( Pt 6): 785-795.
11. Santama N, Krijnse-Locker J, Griffiths G, Noda Y, Hirokawa N, Dotti CG: KIF2beta, a new kinesin superfamily protein in non-neuronal cells, is associated with lysosomes and may be implicated in their centrifugal translocation.EMBO J 1998, 17: 5855-5867.
12. Lee KD, Hollenbeck PJ: Phosphorylation of kinesin in vivo correlates with organelle association and neurite outgrowth.J Biol Chem 1995, 270: 5600-5605.
13. Marlowe KJ, Farshori P, Torgerson RR, Anderson KL, Miller LJ, McNiven MA: Changes in kinesin distribution and phosphorylation occur during regulated secretion in pancreatic acinar cells.Eur J Cell Biol 1998, 75: 140-152.
14. Matthies HJ, Miller RJ, Palfrey HC: Calmodulin binding to and cAM P-dependent phosphorylation of kinesin light chains modulate kinesin ATPase activity.J Biol Chem 1993, 268: 11176-11187. 15. Sato-Yoshitake R, Yorifuji H, Inagaki M, Hirokawa N: The phosphorylation of kinesin regulates its
binding to synaptic vesicles.J Biol Chem 1992, 267: 23930-23936.
16. Deacon SW, Serpinskaya AS, Vaughan PS, Lopez FM, Vernos I, Vaughan KT et al.: Dynactin is required for bidirectional organelle transport.J Cell Biol 2003, 160: 297-301.
17. Holzbaur EL, Vallee RB: DYNEINS: molecular structure and cellular function.Annu Rev Cell Biol 1994, 10: 339-372.
18. Paschal BM, Shpetner HS, Vallee RB: M AP 1C is a microtubule-activated ATPase which translocates microtubules in vitro and has dynein-like properties.J Cell Biol 1987, 105: 1273-1282.
19. Niclas J, Allan VJ, Vale RD: Cell cycle regulation of dynein association with membranes modulates microtubule-based organelle transport.J Cell Biol 1996, 133: 585-593.
20. Vaughan PS, Leszyk JD, Vaughan KT: Cytoplasmic dynein intermediate chain phosphorylation regulates binding to dynactin.J Biol Chem 2001, 276: 26171-26179.
21. Rogers SL, Tint IS, Fanapour PC, Gelfand VI: Regulated bidirectional motility of melanophore pigment granules along microtubules in vitro.Proc Natl Acad Sci U S A 1997, 94: 3720-3725. 22. Kumar S, Lee IH, Plamann M: Cytoplasmic dynein ATPase activity is regulated by
dynactin-dependent phosphorylation.J Biol Chem 2000, 275: 31798-31804.
25. Meresse S, Gorvel JP, Chavrier P: The rab7 GTPase resides on a vesicular compartment connected to lysosomes. J Cell Sci 1995, 108 ( Pt 11): 3349-3358.
26. Vitelli R, Santillo M, Lattero D, Chiariello M, Bifulco M, Bruni CB et al.: Role of the small GTPase Rab7 in the late endocytic pathway. J Biol Chem 1997, 272: 4391-4397.
27. Cantalupo G, Alifano P, Roberti V, Bruni CB, Bucci C: Rab-interacting lysosomal protein (RILP): the Rab7 effector required for transport to lysosomes. EMBO J 2001, 20: 683-693.
28. Jordens I, Fernandez-Borja M, Marsman M, Dusseljee S, Janssen L, Calafat J et al.: The Rab7 effector protein RILP controls lysosomal transport by inducing the recruitment of dynein-dynactin motors. Curr Biol 2001, 11: 1680-1685.
29. Holleran EA, Ligon LA, Tokito M, Stankewich MC, Morrow JS, Holzbaur EL: BetaIII spectrin binds to the Arp1 subunit of dynactin. J Biol Chem 2001.
30. Muresan V, Stankewich MC, Steffen W, Morrow JS, Holzbaur EL, Schnapp BJ: Dynactin-Dependent, Dynein-Driven Vesicle Transport in the Absence of Membrane Proteins. A Role for Spectrin and Acidic Phospholipids. Mol Cell 2001, 7: 173-183.
31. Hoepfner S, Severin F, Cabezas A, Habermann B, Runge A, Gillooly D et al.: Modulation of receptor recycling and degradation by the endosomal kinesin KIF16B. Cell 2005, 121: 437-450.
32. Seabra MC, Coudrier E: Rab GTPases and myosin motors in organelle motility. Traffic 2004, 5: 393-399.
33. Chabrillat ML, Wilhelm C, Wasmeier C, Sviderskaya EV, Louvard D, Coudrier E: Rab8 Regulates the Actin-based Movement of Melanosomes. Mol Biol Cell 2005.
34. Fukuda M, Kuroda TS, Mikoshiba K: Slac2-a/melanophilin, the missing link between Rab27 and myosin Va: implications of a tripartite protein complex for melanosome transport. J Biol Chem 2002, 277: 12432-12436.
35. Hume AN, Collinson LM, Hopkins CR, Strom M, Barral DC, Bossi G et al.: The leaden gene product is required with Rab27a to recruit myosin Va to melanosomes in melanocytes. Traffic 2002, 3: 193-202.
36. Nagashima K, Torii S, Yi Z, Igarashi M, Okamoto K, Takeuchi T et al.: Melanophilin directly links Rab27a and myosin Va through its distinct coiled-coil regions. FEBS Lett 2002, 517: 233-238. 37. Westbroek W, Lambert J, Bahadoran P, Busca R, Herteleer MC, Smit N et al.: Interactions of human
Myosin Va isoforms, endogenously expressed in human melanocytes, are tightly regulated by the tail domain. J Invest Dermatol 2003, 120: 465-475.
38. Wu X, Rao K, Bowers MB, Copeland NG, Jenkins NA, Hammer JA, III: Rab27a enables myosin Va-dependent melanosome capture by recruiting the myosin to the organelle. J Cell Sci 2001, 114: 1091-1100.
39. Gomez PF, Luo D, Hirosaki K, Shinoda K, Yamashita T, Suzuki J et al.: Identification of rab7 as a melanosome-associated protein involved in the intracellular transport of tyrosinase-related protein 1. J Invest Dermatol 2001, 117: 81-90.
40. Hirosaki K, Yamashita T, Wada I, Jin HY, Jimbow K: Tyrosinase and tyrosinase-related protein 1 require Rab7 for their intracellular transport. J Invest Dermatol 2002, 119: 475-480.
41. Gross SP, Tuma MC, Deacon SW, Serpinskaya AS, Reilein AR, Gelfand VI: Interactions and regulation of molecular motors in Xenopus melanophores. J Cell Biol 2002, 156: 855-865.
42. Araki K, Horikawa T, Chakraborty AK, Nakagawa K, Itoh H, Oka M et al.: Small Gtpase rab3A is associated with melanosomes in melanoma cells. Pigment Cell Res 2000, 13: 332-336.
43. Yi Z, Yokota H, Torii S, Aoki T, Hosaka M, Zhao S et al.: The Rab27a/granuphilin complex regulates the exocytosis of insulin-containing dense-core granules. Mol Cell Biol 2002, 22: 1858-1867.
44. Fukuda M: Distinct Rab binding specificity of Rim1, Rim2, rabphilin, and Noc2. Identification of a critical determinant of Rab3A/Rab27A recognition by Rim2. J Biol Chem 2003, 278: 15373-15380. 45. Knodler LA, Steele-Mortimer O: Taking possession: biogenesis of the Salmonella-containing
vacuole. Traffic 2003, 4: 587-599.
46. Meresse S, Steele-Mortimer O, Moreno E, Desjardins M, Finlay B, Gorvel JP: Controlling the maturation of pathogen-containing vacuoles: a matter of life and death. Nat Cell Biol 1999, 1: E183-E188.
47. Guignot J, Caron E, Beuzon C, Bucci C, Kagan J, Roy C et al.: Microtubule motors control membrane dynamics of Salmonella-containing vacuoles. J Cell Sci 2004, 117: 1033-1045.
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49. Raffatellu M, Wilson RP, Chessa D, Andrews-Polymenis H, Tran QT, Lawhon S et al.: SipA, SopA, SopB, SopD, and SopE2 contribute to Salmonella enterica serotype typhimurium invasion of epithelial cells. Infect Immun 2005, 73: 146-154.
50. Waterman SR, Holden DW: Functions and effectors of the Salmonella pathogenicity island 2 type III secretion system. Cell Microbiol 2003, 5: 501-511.
51. Williams C, Galyov EE, Bagby S: solution structure, backbone dynamics, and interaction with Cdc42 of Salmonella guanine nucleotide exchange factor SopE2. Biochemistry 2004, 43: 11998-12008.
52. Harrison RE, Brumell JH, Khandani A, Bucci C, Scott CC, Jiang X et al.: Salmonella impairs RILP recruitment to Rab7 during maturation of invasion vacuoles. Mol Biol Cell 2004, 15: 3146-3154. 53. Wang T, Wong KK, Hong W: A unique region of RILP distinguishes it from its related proteins in
its regulation of lysosomal morphology and interaction with Rab7 and Rab34. Mol Biol Cell 2004, 15: 815-826.
54. Wu M, Wang T, Loh E, Hong W, Song H: Structural basis for recruitment of RILP by small GTPase Rab7. EMBO J 2005, 24: 1491-1501.
55. Colucci AM, Campana MC, Bellopede M, Bucci C: The Rab-interacting lysosomal protein, a Rab7 and Rab34 effector, is capable of self-interaction. Biochem Biophys Res Commun 2005, 334: 128-133.
56. Caplan S, Hartnell LM, Aguilar RC, Naslavsky N, Bonifacino JS: Human Vam6p promotes lysosome clustering and fusion in vivo. J Cell Biol 2001, 154: 109-122.
57. Poupon V, Stewart A, Gray SR, Piper RC, Luzio JP: The role of mVps18p in clustering, fusion, and intracellular localization of late endocytic organelles. Mol Biol Cell 2003, 14: 4015-4027.
58. Huizing M, Didier A, Walenta J, Anikster Y, Gahl WA, Kramer H: Molecular cloning and characterization of human VPS18, VPS 11, VPS16, and VPS33. Gene 2001, 264: 241-247.
59. Richardson SC, Winistorfer SC, Poupon V, Luzio JP, Piper RC: Mammalian late vacuole protein sorting orthologues participate in early endosomal fusion and interact with the cytoskeleton.Mol Biol Cell 2004, 15: 1197-1210.
60. Sato TK, Rehling P, Peterson MR, Emr SD: Class C Vps protein complex regulates vacuolar SNARE pairing and is required for vesicle docking/fusion. Mol Cell 2000, 6: 661-671.
61. Wurmser AE, Sato TK, Emr SD: New component of the vacuolar class C-Vps complex couples nucleotide exchange on the Ypt7 GTPase to SNARE-dependent docking and fusion. J Cell Biol 2000, 151: 551-562.
62. Woodman PG: Biogenesis of the sorting endosome: the role of Rab5. Traffic 2000, 1: 695-701. 63. Stein MP, Feng Y, Cooper KL, Welford AM, Wandinger-Ness A: Human VPS34 and p150 are Rab7
interacting partners. Traffic 2003, 4: 754-771.
64. Mizuno K, Kitamura A, Sasaki T: Rabring7, a novel Rab7 target protein with a RING finger motif. Mol Biol Cell 2003, 14: 3741-3752.
65. Nielsen E, Severin F, Backer JM, Hyman AA, Zerial M: Rab5 regulates motility of early endosomes on microtubules. Nat Cell Biol 1999, 1: 376-382.
66. Koppelman B, Neefjes JJ, de Vries JE, de Waal MR: Interleukin-10 down-regulates MHC class II alphabeta peptide complexes at the plasma membrane of monocytes by affecting arrival and recycling. Immunity 1997, 7: 861-871.
67. Benjamin D, Knobloch TJ, Dayton MA: Human B-cell interleukin-10: B-cell lines derived from patients with acquired immunodeficiency syndrome and Burkitt's lymphoma constitutively secrete large quantities of interleukin-10. Blood 1992, 80: 1289-1298.
