Effect of Calmodulin Antagonists on Endocytosis and Intracellular Transport of Ricin in Polarized MDCK Cells

Llorente, Alicia; Garred, Øystein; Holm, Pernille; Eker, Per; Jacobsen, Johanne T.; Deurs, Bo van; Sandvig, Kirsten

doi:10.1006/excr.1996.0279

Cited by 33 publications

(46 citation statements)

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“…This result indicates that RII␣ is a strong regulator of the transport of ricin from the plasma membrane to the Golgi apparatus. Earlier studies have demonstrated that calmodulin (26) and calcium (27) can modulate the transport of ricin from endosomes to the Golgi apparatus in other cell lines (Fig. 9).…”

Section: Discussionmentioning

confidence: 77%

Endosome-to-Golgi Transport Is Regulated by Protein Kinase A Type IIα

Birkeli

Llorente

Torgersen

et al. 2003

Journal of Biological Chemistry

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Studies of RII␣-deficient B lymphoid cells and stable transfectants expressing the type II␣ regulatory subunit (RII␣) of cAMP-dependent protein kinase (PKA), which is targeted to the Golgi-centrosomal area, reveal that the presence of a Golgi-associated pool of PKA type II␣ mediates a change in intracellular transport of the plant toxin ricin. The transport of ricin from endosomes to the Golgi apparatus, measured as sulfation of a modified ricin (ricin sulf-1), increased in RII␣-expressing cells when PKA was activated. However, not only endosometo-Golgi transport, but also retrograde ricin transport to the endoplasmic reticulum (ER), measured as sulfation and N-glycosylation of another modified ricin (ricin sulf-2), seemed to be increased in cells expressing RII␣ in the presence of a cAMP analog, 8-(4-chlorophenylthio)-cAMP. Thus, PKA type II␣ seems to be involved in both endosome-to-Golgi and Golgi-to-ER transport. Because ricin, after being retrogradely transported to the ER, is translocated to the cytosol, where it inhibits protein synthesis, we also investigated the influence of RII␣ expression on ricin toxicity. In agreement with the other data obtained, 8-(4-chlorophenylthio)-cAMP and RII␣ were found to sensitize cells to ricin, indicating an increased transport of ricin to the cytosol. In conclusion, our results demonstrate that transport of ricin from endosomes to the Golgi apparatus and further to the ER is regulated by PKA type II␣ isozyme.

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Section: Discussionmentioning

confidence: 77%

Endosome-to-Golgi Transport Is Regulated by Protein Kinase A Type IIα

Birkeli

Llorente

Torgersen

et al. 2003

Journal of Biological Chemistry

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“…Calmodulin emerges as a pivotal molecule for most of the functions accomplished in the heterogeneous ''recycling-endosomes''; it is involved in the recycling of transferrin and pIgR, in the transcytosis of pIgA, 60 in the endocytosis and recycling of ricin, 65 and it is also crucial in the regulation of several activities shown in caveolae. 66 It is remarkable that receptors for transferrin, 67 pIgA, 60,68 insulin, 69 and epidermal growth factor 70 are calmodulin-binding proteins.…”

Section: Intracellular Organization and Molecular Mechanisms On Rrc Fmentioning

confidence: 99%

Dissection of the multifunctional “receptor-recycling” endocytic compartment of hepatocytes

et al. 1999

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“…Also, in polarized MDCK cells transport of ricin from endosomes to the Golgi apparatus is independently regulated at the two poles (Llorente et al, 1996(Llorente et al, , 1998b. The existence of pathways mediating transport of TGN38 either directly from EE or via the perinuclear endosomal recycling compartment (ERC) to the TGN has been proposed (Ghosh et al, 1998;Mallet and Maxfield, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Different transport routes between endosomes and the TGN have been suggested based on identification of proteins common to both endosomes and the TGN (Gruenberg and Maxfield, 1995;Mukherjee et al, 1997). Also, in polarized MDCK cells transport of ricin from endosomes to the Golgi apparatus is independently regulated at the two poles (Llorente et al, 1996(Llorente et al, , 1998b. The existence of pathways mediating transport of TGN38 either directly from EE or via the perinuclear endosomal recycling compartment (ERC) to the TGN has been proposed (Ghosh et al, 1998;Mallet and Maxfield, 1999).…”

Section: Introductionmentioning

confidence: 99%

Endosome to Golgi Transport of Ricin Is Independent of Clathrin and of the Rab9- and Rab11-GTPases

Iversen

Skretting

Llorente

et al. 2001

MBoC

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The plant toxin ricin is transported to the Golgi and the endoplasmic reticulum before translocation to the cytosol where it inhibits protein synthesis. The toxin can therefore be used to investigate pathways leading to the Golgi apparatus. Except for the Rab9-mediated transport of mannose 6-phosphate receptors from endosomes to the trans-Golgi network (TGN), transport routes between endosomes and the Golgi apparatus are still poorly characterized. To investigate endosome to Golgi transport, we have used here a modified ricin molecule containing a tyrosine sulfation site and quantified incorporation of radioactive sulfate, a TGN modification. A tetracycline-inducible mutant Rab9S21N HeLa cell line was constructed and characterized to study whether Rab9 was involved in transport of ricin to the TGN and, if not, to further investigate the route used by ricin. Induced expression of Rab9S21N inhibited Golgi transport of mannose 6-phosphate receptors but did not affect the sulfation of ricin, suggesting that ricin is transported to the TGN via a Rab9-independent pathway. Moreover, because Rab11 is present in the endosomal recycling compartment and the TGN, studies of transient transfections with mutant Rab11 were performed. The results indicated that routing of ricin from endosomes to the TGN occurs by a Rab11-independent pathway. Finally, because clathrin has been implicated in early endosome to TGN transport, ricin transport was investigated in cells with inducible expression of antisense to clathrin heavy chain. Importantly, endosome to TGN transport (sulfation of endocytosed ricin) was unchanged when clathrin function was abolished. In conclusion, ricin is transported from endosomes to the Golgi apparatus by a Rab9-, Rab11-, and clathrin-independent pathway. INTRODUCTIONIntoxication of cells with the plant toxin ricin involves endocytosis and retrograde transport of the toxin to the transGolgi network (TGN) and the endoplasmic reticulum (ER) before translocation of the enzymatically active subunit (the A fragment) to the cytosol takes place Wesche et al., 1999). The precise site at which ricin leaves the endocytic pathway to target the TGN is still unknown, and ricin has been localized in endosomes as well as in lysosomes (van Deurs et al., 1988).One well-characterized transport route from late endosomes (LE) to the TGN is utilized by mannose 6-phosphate receptors (M6PRs), binding mannose 6-phosphate-tagged proteins at the TGN and delivering them to LE (Goda and Pfeffer, 1988;Munier-Lehmann et al., 1996). At steady state, the receptors accumulate in these two compartments although they are also found to a lesser extent on the plasma membrane and in early endosomes (EE) (Kornfeld and Mellman, 1989). Ligand dissociation occurs at the low pH of LE, from where the uncharged receptors recycle back to the TGN by a pathway dependent on the small GTPase Rab9 (Lombardi et al., 1993;Riederer et al., 1994).Several lines of evidence suggest that there is more than one transport route from endosomes to the Golgi apparatus. Di...

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Effect of Calmodulin Antagonists on Endocytosis and Intracellular Transport of Ricin in Polarized MDCK Cells

Cited by 33 publications

References 0 publications

Endosome-to-Golgi Transport Is Regulated by Protein Kinase A Type IIα

Endosome-to-Golgi Transport Is Regulated by Protein Kinase A Type IIα

Dissection of the multifunctional “receptor-recycling” endocytic compartment of hepatocytes

Endosome to Golgi Transport of Ricin Is Independent of Clathrin and of the Rab9- and Rab11-GTPases

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