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Relationship: 993


A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Disruption, Lysosome leads to N/A, Mitochondrial dysfunction 1

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes. Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
Endocytic lysosomal uptake leading to liver fibrosis adjacent High Allie Always (send email) Under development: Not open for comment. Do not cite EAGMST Under Review

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER.  More help
Term Scientific Term Evidence Link
human Homo sapiens High NCBI
mouse Mus musculus Moderate NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER.  More help
Term Evidence
All life stages

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Disrupted lysosomal membrane release the content of lysosomes including cathepsins. Cathepsins take part in activation of BH3-only proteins, which directly or indirectly activate pro-apoptic Bax and Bak proteins. Once activated Bax and Bak form dimers and higher order oligomers, in order to form pores in outer mitochondrial membrane and cause mitochondrial injury.

Many evidences suggest that lysosomal disruption usually precedes mitochondrial injury (Guicciardi et al., 2000; Brunk et al., 2001; Zhao et al. 2003; Droga-Mazovec et al., 2008), with lysosomal proteases inducing mitochondrial dysfunction.

Zhao and colleagues have also proposed the existence of a positive feed-back mechanism between lysosomal damage and mitochondrial damage, in which early lysosomal rupture causes mitochondrial rupture and leakage of mitochondrial proteins that increase lysosomal damage and consequent apoptosis (Zhao et al., 2000).

The pathway between lysosomal membrane permeabilization (LMP) and mitochondrial membrane permeabilization (MMP) is regulated principally by Bcl-2 family of proteins. The family is subdivided into anti-apoptotic multidomain proteins (such as Bcl-2, Bcl-xl, Bcl-W, Mcl-1 and A1), pro-apoptotic multidomain proteins (Bax and Bak) and pro-apoptotic BH3-only proteins (such as Bid, Puma, Noxa, Bim, Bad, and Bik) (Fletcher and Huang, 2006; Youle and Strasser, 2008).

Cathepsins, released after lysosomal damage, have a role in the cell death through the cleavage of BH3-only proteins, such as Bid, to generate active tBid (truncated Bid) (Blomgran et al., 2007; Cirman et al., 2004; Droga-Mazovec et al., 2008; Houseweart et al., 2003; Stoka et al., 2001) and by degradation of the anti-apoptotic Bcl-2 molecules Bcl-2, Bcl-xl and Mcl-1 (Blomgran et al., 2007; Droga-Mazovec et al., 2008). However it was shown that though Bid is not the only substrate of lysosomal enzymes that induce cytochrome c release, it is the major one (Stoka et al., 2001). Droga-Mazovec and colleagues showed that Bid is cleaved by cathepsins in human liver carcinoma cells (HepG2) (Droga-Mazovec et al., 2008), while other study showed that particularly cathepsin B is active in hepatocytes (Guicciardi et al., 2000).

Bid is also cleaved by caspase 8, which represents a link between extrinsic and intrinsic (mitochondrial) pathway (Li et al., 1998).

Activated BH3-only proteins continue to activate pro-apoptic proteins Bax and Bak. Sarosiek et al. observed that Bid preferentially activates Bak, while Bim activates Bax (Sarosiek et al., 2013). The activation of Bax and Bak occurs after LMP, but before mitochondrial release of cytochrome c and caspase-3 activation (Boya et al., 2003). Currently there are two models describing activation of Bax and Bak proteins and the role of anti-apoptic and pro-apoptic multidomain proteins in it. In the indirect model, Bax and Bak are sequestered and inactivated by anti-apoptotic Bcl-2 proteins. The binding of pro-apoptotic BH3-only proteins to these Bcl-2 proteins triggers the release of Bax and Bak. The direct model proposes that Bax and Bak are activated by direct binding of pro-apoptotic BH3-only proteins, called the activators (Bid, Bim or Puma). However, these activators are normally sequestered by anti-apoptotic Bcl-2 proteins. In order to release the activators, other BH3-only proteins, called senzitizers, neutralize anti-apoptotic Bcl-2 proteins (Brenner and Mak, 2009; Willis et al., 2007).

Bak and Bax go under major conformational changes after binding of BH3 only proteins (as reviewed by Westphal et al., 2014). Once activated Bak or Bax molecules bind reciprocally to form symmetric homodimers. It is thought that homodimers of Bak or Bax must then associate to higher order oligomers to porate the mitochondrial outer membrane (Uren et al., 2017). Heterodimers form only a minor population compared with homodimers (Dewson et al., 2012; Mikhailov et al., 2003).

Bak and Bax shallow insertion into the outer leaflet of mitochondrial membrane (Westphal et al., 2014; Oh KJ et al., 2010) may destabilize the lamellar structure of the bilayer to induce lipidic pores in mitochondrial membrane. This induces release of proteins from the space between inner and outer mitochondrial membrane (Newmeyer et al., 2003).

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER.  For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings.  Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help
Biological Plausibility
Addresses the biological rationale for a connection between KEupstream and KEdownstream.  This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured.   More help

In the last decade there is a growing body of evidences about the strong functional link between lysosomes and mitochondria that play an important role in physiology and pathology. The evidences also showed link between lysosomal and mitochondrial damage, and that lysosomal damage precedes mitochondrial injury.

Uncertainties and Inconsistencies
Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

Repnik and colleagues showed that inhibition of cysteine cathepsins by E-64-d had little effect on LDH (cytosolic enzyme lactate dehydrogenase) release in medium in LLOMe treated cells (Repnik et al., 2017). They also detected that after exposure to LLOMe, cathepsins remain in lysosomes and are being degraded there which is in contradiction with most of the previous studies.

As stated earlier there are empirical evidences that incubation of cathepsin B with mitochondria and cytosolic factors increase mitochondrial permeabilization. However, in some studies pharmacological inhibition of cathepsin B, L and D didn't suppress Bid cleavage, suggesting that other lysosomal proteases might be responsible for Bid cleavage (Reiners et al., 2002).

The knockout of genes coding for cathepsins B, D, L and S failed to prevent induced MMP and cell death (Boya et al., 2003).

Housewert et al. showed that the amount of cerebellar granule cell apoptosis in cystatin B-deficient mice did not change when Bid was removed.  This indicates that cathepsins can use other mechanisms to initiate apoptosis. They concluded that another molecule may partially substitute for Bid when it is missing (Housewert et al., 2003). Willis and colleagues showed that neither Bim nor Bid are necessary for apoptosis, as their absences didn't stop apoptosis or prevented Bax activation (Willis et al., 2007).

Some  reports described Bax/Bak-independent mechanisms of cytochrome c release, involving either cyclosporine A sensitive mitochondrial membrane permeability (Wan et al., 2008) or a serine protease(s)-dependent mechanism (Mizuta et al., 2007).

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references.  More help
Response-response Relationship
Provides sources of data that define the response-response relationships between the KEs.  More help
Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help
Known Feedforward/Feedback loops influencing this KER
Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

Murine (Stoka et al., 2001; Zhang et al., 2009; Lindsten et al., 2000)

Human (Boya et al., 2003; Cirman et al., 2004)


List of the literature that was cited for this KER description. More help

Baixauli F, Acin-Perez R, Villarroya-Beltri C, Mazzeo C, Nunez-Andrade N, Gabande-Rodriguez E, Ledesma MD, Blázquez A, Martin MA, Falcón-Pérez JM, Redondo JM, Enríquez JA, Mittelbrunn M. Mitochondrial respiration controls lysosomal function during inflammatory T cell responses. Cell Metab. (2015) 22, 485–498.

Bidere N, Lorenzo HK,  Carmona S, Laforge M, Harper F, Dumont C, Senik A. Cathepsin D triggers Bax activation, resulting in selective AIF relocation in T lymphocytes entering the early commitment phase to apoptosis. J. Biol. Chem. (2003) 278:31401–31411.

Blomgran R, Zheng L, Stendah O. Cathepsin-cleaved Bid promotes apoptosis in human neutrophils via oxidative stress-induced lysosomal membrane permeabilization, J. Leukoc. Biol. (2007) 81 1213–1223.

Boya P, Andreau K, Poncet D, Zamzami N, Perfettini JL, Metivier D, Ojcius DM, Jäättelä M, Kroemer G. Lysosomal membrane permeabilization induces cell death in a mitochondrion-dependent fashion. J. Exp. Med. (2003) 197:1323–1334.

Brenner D, Mak TW. Mitochondrial cell death effectors.  Curr Opin Cell Biol. (2009) 21(6): 871–877.

Brunk UT, Dalen H, Roberg K, Hellquist HB. Photo-oxidative disruption of lysosomal membranes causes apoptosis of cultured human fibroblasts. Free Radicals Biol. Med. (1997) 23, 61 -626.

Cirman T, Orešić K, Mazovec GD, Turk V, Reed JC, Myers RM, Salvesen GS, Turk B. Selective disruption of lysosomes in HeLa cells triggers apoptosis mediated by cleavage of Bid by multiple papain-like lysosomal cathepsins, J. Biol. Chem. 279 (2004) 3578–3587.

Dewson G, Ma S, Frederick P, Hockings C, Tan I, Kratina T, Kluck RM. Bax dimerizes via a symmetric BH3:groove interface during apoptosis. Cell Death Differ. (2012) 19, 661–670.

Droga-Mazovec G, Bojič L, Petelin A, Ivanova S, Romih R, Repnik U, Salvesen GS, Stoka V, Turk V, Turk B. Cysteine cathepsins trigger caspase-dependent cell death through cleavage of bid and antiapoptotic Bcl-2 homologues, J. Biol. Chem. (2008)  283: 19140–19150.

Fernandez-Mosquera L, Diogo CV, Yambire KF, Santos GL, Luna Sanchez M, Benit P, Rustin P, Lopez LC, Milosevic I, Raimundo N. Acute and chronic mitochondrial respiratory chain deficiency differentially regulate lysosomal biogenesis. Sci. Rep. (2017) 7:45076.

Fletcher JI, Huang DC. BH3-only proteins: orchestrating cell death. Cell Death Differ. (2006) 13: 1268-1271.

Ghosh M, Carlsson F, Laskar A, Yuang XM, Li W. Lysosomal membrane permeabilization causes oxidative stress and ferritin induction in macrophages. FEBS Lett. (2011) 585(4): 623–629.

Gross A, Yin XM, Wang K, Wei MC, Jockel J, Milliman C, Erdjument-Bromage H, Tempst P, Korsmeyer SJ. Caspase cleaved BID targets mitochondrial and is required for cytochrome c release, while BCL-XL prevents this release but not tumor necrosis factor-R1/Fas death. J. Biol. Chem. (1999) 274: 1156 ± 1163.

Guicciardi ME,  Deussing J, Miyoshi H, Bronk SF, Svingen PA, Peters C, Kaufmann SH, Gores GJ. Cathepsin B contributes to TNF-alpha-mediated hepatocyte apoptosis by promoting mitochondrial release of cytochrome c. J. Clin. Invest. (2000) 106:1127–1137.

Houseweart MK, Vilaythong A, Yin XM, Turk B, Noebels JL, Myers RM. Apoptosis caused by cathepsins does not require Bid signaling in an in vivo model of progressive myoclonus epilepsy (EPM1). Cell Death and Differentiation, (2003): 10(12), 1329-1335.

Jürgensmeier JM, Xie Z, Deveraux Q, Ellerby L, Bredesen D, Reed JC.  Bax directly induces release of cytochrome c from isolated mitochondria. Proc Natl Acad Sci U S A. (1998) 95(9): 4997–5002.

Kagedal K, Zhao M, Svensson I, Brunk UT. Sphingosine-induced apoptosis is dependent on lysosomal proteases. The Biochemical journal.  (2001) 359: 335-43.

Korsmeyer SJ, Wei MC, Saito M, Weiler S, Oh KJ, Schlesinger PH. Pro-apoptotic cascade activates BID, which oligomerizes BAK or BAX into pores that result in the release of cytochrome c.  Cell Death Differ. (2000); 7(12): 1166–1173.

Li H, Zhu H, Xu CJ, Yuan J. Cleavage of BID by caspase 8 mediates the mitochondrial damage in the Fas pathway of apoptosis. Cell. (1998) 94(4): 491–501.

Lindsten T, Ross AJ, King A, Zong WX, Rathmell JC, Shiels HA, Ulrich E, Waymire KG, Mahar P, Frauwirth K, Chen Y, Wei M, Eng VM, Adelman DM, Simon MC, Ma A, Golden JA, Evan G, Korsmeyer SJ, MacGregor GR, Thompson  CB. The combined functions of proapoptotic Bcl-2 family members bak and bax are essential for normal development of multiple tissues. Mol. Cell. (2000) 6: 1389–1399.

Luo X, Budihardjo I, Zou H, Slaughter C, Wang X. Bid, aBcl2 interacting protein, mediates cytochrome c release from mitochondria in response to activation of cell surface death receptors. Cell (1998) 94: 481 - 490.

Mikhailov V, Mikhailova M, Degenhardt K, Venkatachalam MA, White E, Saikumar P. Association of Bax and Bak homo-oligomers in mitochondria. Bax requirement for Bak reorganization and cytochrome c release. J. Biol. Chem. (2003) 278: 5367–5376.

Mizuta T, Shimizu S, Matsuoka Y, Nakagawa T, Tsujimoto Y. A Bax/Bak-independent mechanism of cytochrome c release. J. Biol. Chem. (2007) 282, 16623–16630.

Newmeyer DD, Ferguson-Miller S. Mitochondria: releasing power for life and unleashing the machineries of death. Cell (2003) 112: 481–490.

Oh KJ, Singh P, Lee K, Foss K, Lee S, Park M, Lee S, Aluvila S, Park M, Singh P, Kim RS, Symersky J, Walters DE. Conformational Changes in BAK, a Pore-forming Proapoptotic Bcl-2 Family Member, upon Membrane Insertion and Direct Evidence for the Existence of BH3-BH3 Contact Interface in BAK Homo-oligomers. The Journal of Biological Chemistry. (2010) 285(37):28924-28937.

Palmieri M, Impey S, Kang H, di Ronza A, Pelz C, Sardiello M, Ballabio A. Characterization of the CLEAR network reveals an integrated control of cellular clearance pathways. Hum. Mol. Genet. (2011).  20: 3852–3866.

Reiners J, Caruso J, Mathieu P, Chelladurai B, Yin X-M, Kessel D. Release of cytochrome c and activation of pro-caspase-9 following lysosomal photodamage involves bid cleavage. Cell death and differentiation. (2002) 9(9):934-944.

Repnik U, Borg Distefano M,  Speth MT, Ng MYW, Progida C, Hoflack B, Gruenberg J, Griffiths G. L-leucyl-L-leucine methyl ester does not release cysteine cathepsins to the cytosol but inactivates them in transiently permeabilized lysosomes. J. Cell Sci. (2017) 130: 3124–3140.

Roberg K, Johansson U, Ollinger K. Lysosomal release of cathepsin D precedes relocation of cytochrome c and loss of mitochondrial transmembrane potential during apoptosis induced by oxidative stress. Free Radic Biol Med. (1999) 27(11-12): 1228–1237.

Roberg K, Kagedal K, Ollinger K. Microinjection of cathepsin d induces caspase-dependent apoptosis in fibroblasts. Am. J. Pathol. (2002) 161:89–96.

Sarosiek KA, Chi X, Bachman JA, Sims JJ, Montero J, Patel L, Flanagan A, Andrews DW, Sorger P, Letai A. BID preferentially activates BAK while BIM preferentially activates BAX, affecting chemotherapy response Mol Cell. Mol Cell. (2013) 51(6): 751–765.

Settembre C, Zoncu R, Medina DL, Vetrini F, Erdin S, Huynh T, Ferron M, Karsenty G, Vellard MC, Facchinetti V, Sabatini DM, Ballabio A. A lysosome-to-nucleus signalling mechanism senses and regulates the lysosome via mTOR and TFEB. EMBO J. (2012) 31, 1095–1108.

Stoka V, Turk B, Schendel SL, Kim TH, Cirman T, Snipas SL, Ellerby LM, Bredesen D, Freeze H, Abrahamson M, BroÈmme D, Krajewski S, Reed JC, Yin XM, Turk V, Salvesen GS. Lysosomal protease pathways to apoptosis: cleavage of Bid, not pro-caspases, is the most likely route. J. Biol. Chem. )2001) 276: 3149 - 3157.

Uren RT, Iyer S, Kluck RM. Pore formation by dimeric Bak and Bax: an unusual pore? Philosophical Transactions of the Royal Society B: Biological Sciences. (2017) 372(1726):20160218.

Wan KF, Chan S-L, Sukumaran SK, Lee M-C, Yu VC. Chelerythrine Induces Apoptosis through a Bax/Bak-independent Mitochondrial Mechanism. The Journal of Biological Chemistry. (2008) 283(13):8423-8433.

Wei MC, Lindsten T, Mootha VK, Weiler S, Gross A, Ashiya M, Thompson CB, Korsmeyer SJ. tBID, a membrane targeted death ligand, oligomerizes BAK to release cytochrome c. Genes Dev. (2000) 14: 2060 -2071.

Westphal D, Kluck RM, Dewson G. Building blocks of the apoptotic pore: how Bax and Bak are activated and oligomerize during apoptosis. Cell Death Differ. (2014) 21: 196–205.

Willis SN, Fletcher JI, Kaufmann T, van Delft MF, Chen L, Czabotar PE, Ierino H, Lee EF, Fairlie WD, Philippe Bouillet, Strasser A, Kluck RM, Adams JM, Huang DCS. Apoptosis initiated when BH3 ligands engage multiple Bcl-2 homologs, not Bax or Bak.  Science. (2007) 315(5813): 856–859.

Youle RJ, Strasser A. The BCL-2 protein family: opposing activities that mediate cell death.  Nat Rev Mol Cell Biol. (2008) 9(1): 47–59.

Zhang H, Zhong C, Shi L, Guo Y, Fan Z. Granulysin induces cathepsin B release from lysosomes of target tumor cells to attack mitochondria through processing of bid leading to Necroptosis. J Immunol. (2009) 182(11): 6993–7000.

Zhao M, Eaton J W, Brunk UT. Protection against oxidantmediated lysosomal rupture: a new anti-apoptotic activity of Bcl-2? FEBS Lett. (2000) 485: 104–108.

Zhao M, Antunes F, Eaton JW, Brunk UT. Lysosomal enzymes promote mitochondrial oxidant production, cytochrome c release and apoptosis. Eur. J. Biochem. (2003) 270: 3778–3786.