Rab7 Activation by Growth Factor Withdrawal Contributes to the Induction of Apoptosis

Rosales, Kimberly Romero; Peralta, Eigen; Guenther, Garret; Wong, Sylvia C.; Edinger, Aimee L.

doi:10.1091/mbc.e08-09-0911

Cited by 55 publications

(50 citation statements)

References 58 publications

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“…The accumulation of aberrant vesicle clusters instead of class E compartments in vps21D vps4D cells suggests Ypt7 might also be dysfunctional in this circumstance. While we detected no reduction in GTP-bound Ypt7, impaired Rab7 function in animal cells in response to protein kinase C delta inhibition has similarly been shown to occur without a reduction in GTP-bound Rab7 (Romero Rosales et al, 2009). The mechanistic basis for Ypt7 dysfunction resulting from ESCRT disruption remains to be determined, but it is possible that the persistence of Vps21 and CORVET at endosomes interferes with the ability of Ypt7 to activate HOPS assembly due to CORVET and HOPS sharing a common set of core subunits (Peplowska et al, 2007) (Fig.…”

Section: Discussioncontrasting

confidence: 56%

Class E compartments form in response to ESCRT dysfunction in yeast due to hyperactivity of the Vps21 Rab GTPase

Russell

Shideler

Nickerson

et al. 2012

Journal of Cell Science

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SummaryThe endosomal sorting complexes required for transport (ESCRTs) mediate the budding of intralumenal vesicles (ILVs) at late endosomes. ESCRT dysfunction causes drastic changes in endosome morphology, which are manifested in Saccharomyces cerevisiae by the formation of aberrant endosomes known as class E compartments. Except for the absence of ILVs, the mechanistic basis for class E compartment biogenesis is unknown. We used electron microscopy to examine endosomal morphology in response to transient ESCRT inactivation and recovery in yeast expressing the temperature-sensitive mutant vps4 ts allele. Our results show class E compartments accumulate fourfold the amount of membrane normally present at multivesicular bodies and that multivesicular bodies can form directly from class E compartments upon recovery of ESCRT function. We found class E compartment formation requires Vps21, which is orthologous to the Rab5A GTPase in metazoans that promotes fusion of endocytic vesicles with early endosomes and homotypic fusion of early endosomes with one another. We also determined that class E compartments accumulate GTP-bound Vps21 and its effector, the class C core vacuole/endosome tethering (CORVET). Ypt7, the yeast ortholog of Rab7 that in metazoans promotes fusion of late endosomes with lysosomes, also accumulates at class E compartments but without its effector, the homotypic fusion and protein sorting (HOPS), signifying that Ypt7 at class E compartments is dysfunctional. These results suggest that failure to complete Rab5-Rab7 conversion is a consequence of ESCRT dysfunction, which results in Vps21 hyperactivity that drives the class E compartment morphology. Indeed, genetic disruption of Rab conversion without ESCRT dysfunction autonomously drives the class E compartment morphology without blocking ILV budding.

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Section: Discussioncontrasting

confidence: 56%

Class E compartments form in response to ESCRT dysfunction in yeast due to hyperactivity of the Vps21 Rab GTPase

Russell

Shideler

Nickerson

et al. 2012

Journal of Cell Science

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“…Thus, mVps39 may impact Rab7 indirectly by influencing mTOR signaling via the Rag GTPases. Consistent with this model, Rab7 activity is modulated by growth factors that regulate mTOR activity (10). Defining the precise mechanism by which mVps39 promotes lysosomal fusion reactions will require additional studies that may be facilitated by the dominant-negative mVps39 mutant described here.…”

Section: Discussionsupporting

confidence: 53%

“…Our observation that the activated mutant Rab7-Q67L did not reverse TBC1D15-induced fragmentation (Fig. 2, A and B) might be explained by a failure to attain sufficiently high levels of Rab7-Q67L or by the fact that expressing Rab7-Q67L to high levels is toxic (10). Alternatively, nucleotide cycling may be required for full Rab7 function.…”

Section: Discussionmentioning

confidence: 85%

“…Cell Culture and Transfection-FL5.12 cells were maintained at low density in RPMI (Mediatech) supplemented with 10% FCS (Mediatech, Hyclone, or Sigma), 500 pM recombinant mouse IL-3 (BD Pharmingen or eBioscience), 10 GST-RILP Pull-downs-Nucleotides 658 -897 of GenBank TM accession number NM 001029938 (amino acids 220 -299) of the murine RILP protein constituting the Rab7 binding domain of RILP were fused to the C terminus of GST in the pGEX 4T-3 vector (Stratagene). GST-RILP was transformed into Escherichia coli strain BL21.…”

Section: Methodsmentioning

confidence: 99%

“…Autophagy, antigen processing, and pathogen clearance are also Rab7-dependent processes (5)(6)(7)(8)(9). Consistent with its key role in maintaining cellular and organismal homeostasis, Rab7 activity is regulated by extrinsic signals (10), most likely through effects on guanine nucleotide exchange factors (GEFs) 2 and GTPase-activating proteins (GAPs). GEFs activate GTPases by facilitating the exchange of GDP for GTP (reviewed in Refs.…”

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confidence: 99%

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Differential Effects of TBC1D15 and Mammalian Vps39 on Rab7 Activation State, Lysosomal Morphology, and Growth Factor Dependence

Peralta

Martin

Edinger

2010

Journal of Biological Chemistry

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111

106

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The small GTPase Rab7 promotes fusion events between late endosomes and lysosomes. Rab7 activity is regulated by extrinsic signals, most likely via effects on its guanine nucleotide exchange factor (GEF) or GTPase-activating protein (GAP). Based on their homology to the yeast proteins that regulate the Ypt7 GTP binding state, TBC1D15, and mammalian Vps39 (mVps39) have been suggested to function as the Rab7 GAP and GEF, respectively. We developed an effector pull-down assay to test this model. TBC1D15 functioned as a Rab7 GAP in cells, reducing Rab7 binding to its effector protein RILP, fragmenting the lysosome, and conferring resistance to growth factor withdrawal-induced cell death. In a cellular context, TBC1D15 GAP activity was selective for Rab7. TBC1D15 overexpression did not inhibit transferrin internalization or recycling, Rab7-independent processes that require Rab4, Rab5, and Rab11 activation. TBC1D15 was thus renamed Rab7-GAP. Contrary to expectations for a Rab7 GEF, mVps39 induced lysosomal clustering without increasing Rab7 GTP binding. Moreover, a dominantnegative mVps39 mutant fragmented the lysosome and promoted growth factor independence without decreasing Rab7-GTP levels. These findings suggest that a protein other than mVps39 serves as the Rab7 GEF. In summary, although only TBC1D15/Rab7-GAP altered Rab7-GTP levels, both Rab7-GAP and mVps39 regulate lysosomal morphology and play a role in maintaining growth factor dependence.The small GTPase Rab7 facilitates homotypic and heterotypic fusion reactions between late endosomes and lysosomes (1-3). Inhibiting Rab7 function produces lysosomal fragmentation, confers growth factor independence, and promotes transformation in vitro (4). Autophagy, antigen processing, and pathogen clearance are also Rab7-dependent processes (5-9). Consistent with its key role in maintaining cellular and organismal homeostasis, Rab7 activity is regulated by extrinsic signals (10), most likely through effects on guanine nucleotide exchange factors (GEFs) 2 and GTPase-activating proteins (GAPs). GEFs activate GTPases by facilitating the exchange of GDP for GTP (reviewed in Refs. 11,12). GAPs inactivate GTPases by accelerating the hydrolysis of the bound GTP to GDP. The nucleotide binding state regulates GTPase activity because GTPases only associate with their effector proteins when GTP-bound. Effector proteins produce the responses associated with GTPase activation. Several effector proteins for Rab7 have been identified (13-16). Defining the Rab7 GEF and GAP proteins would provide critical insight into how its function is regulated.Because membrane fusion is frequently studied using purified yeast vacuoles, much is known about the molecules that regulate Ypt7, the Rab7 ortholog in Saccharomyces cerevisiae (17)(18)(19). Gyp7 is the Ypt7 GAP, blocking vacuole fusion by promoting GTP hydrolysis by . The GEF for Ypt7 may be Vps39. Vps39 facilitates nucleotide exchange on Ypt7 in vitro (23). However, in other studies, Vps39 preferentially bound the GTP-bound form of Ypt7 sugge...

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A role of Rab7 in stabilizing EGFR‐Her2 and in sustaining Akt survival signal

Wang

Ming

et al. 2012

Journal Cellular Physiology

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Rab7 plays an important role in regulating endocytic traffic. In view of an emerging role of membrane traffic in signaling and diseases, we have examined the possible role of Rab7 in oncogenesis. The role of Rab7 was investigated using shRNA-mediated knockdown in A431 and MCF7 cancer cells. To our surprise, Rab7 knockdown effectively suppressed anchorage-independent growth of cancer cells in soft agar. Anoikis (matrix-detachment triggered apoptosis) was enhanced, while the level of phosphorylated (active) Akt (which is a key survival factor) was significantly reduced. Also intriguing was the observation that EGFR and Her2 levels were significantly reduced when Rab7 was knocked-down. More robust reduction of EGFR and Her2 levels was observed when knocked-down cells were treated with HSP90 inhibitor geldanamycin (GA). Low concentration of GA (50-100 nm)-induced apoptosis of the Rab7 knocked-down cells but not control cells, suggesting that Rab7 and HSP90 together contribute to the optimal stability of EGFR and Her2 as well as to protect cancer cells from apoptosis. Rab7 seems to protect EGFR and Her2 from proteosome-mediated degradation. These results suggest that Rab7 is likely involved in protecting EGFR and Her2 from being degraded by the proteosome and in maintaining optimal Akt survival signal (especially during cell detachment or when HSP90 is inhibited). Rab7 is potentially a novel target for combinatory therapy with Hsp90 inhibitors.

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Rab7 Activation by Growth Factor Withdrawal Contributes to the Induction of Apoptosis

Cited by 55 publications

References 58 publications

Class E compartments form in response to ESCRT dysfunction in yeast due to hyperactivity of the Vps21 Rab GTPase

Class E compartments form in response to ESCRT dysfunction in yeast due to hyperactivity of the Vps21 Rab GTPase

Differential Effects of TBC1D15 and Mammalian Vps39 on Rab7 Activation State, Lysosomal Morphology, and Growth Factor Dependence

A role of Rab7 in stabilizing EGFR‐Her2 and in sustaining Akt survival signal

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