Relationship: 993



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

Upstream event


Disruption, Lysosome

Downstream event


N/A, Mitochondrial dysfunction 1

Key Event Relationship Overview


AOPs Referencing Relationship


AOP Name Adjacency Weight of Evidence Quantitative Understanding
Endocytic lysosomal uptake leading to liver fibrosis adjacent High

Taxonomic Applicability


Term Scientific Term Evidence Link
human Homo sapiens High NCBI
mouse Mus musculus Moderate NCBI

Sex Applicability


Sex Evidence

Life Stage Applicability


Term Evidence
All life stages

Key Event Relationship Description


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 Supporting this KER


Biological Plausibility


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.

Empirical Evidence


LMP after exposure to ciprofloxacine, norfloxacine and hydroxychloroquine is detected couple of hourse earlier that MMP (Boya et al., 2003). The same study proves that the cells with signs of MMP are sub-ensemple of the group of the cells with signs of LMP, not vice-versa. Also inhibition of LMP with Baf A1 – that inhibits lysosomal vacuolar H+ ATP-ase, prevented MMP, while inhibition of MMP in Bax/Bak double knocks out cells didn't prevent LMP. However, inhibition of MMP prevented LMP to cause manifestations of the cell death. All the evidences from this and other studies (such as Droga-Mazovec et al., 2008; Ghosh et al., 2011) prove that LMP lies upstream from MMP and causes it.

When isolated mitochondria are incubated with purified cathepsin B in the presence of cytolic extracts, a release of cytochrome c from mitochondria is detected (Guicciardi et al., 2000). The microinjection of cathepsin D to the cell causes cytochrome c release, capsases activation and apoptosis (Roberg et al., 2002).

It was shown that mice deficient of stefin B (major intracellular cathepsins inhibitor) developed spontaneous cerebellar apoptosis (Houseweart et al., 2003). Pepstatin A, an inhibitor of cathepsin D, was found to inhibit caspase-3-like proteolytic activity and to prevent apoptosis (Roberg et al., 1999). The treatment of the cells with cathepsin B and cathepsin D inhibitors, pepstatin A and E-64-d, decreased MMP and activation of caspases (Kagedal et al., 2001).

Cathepsin B directly cuts Bid and produces active tBid, while cathepsin B inhibitors z-FA-fmk and E-64-d block Bid activation in cells (Zhang et al., 2009; Blomgran et al., 2007). When cathepsin B silenced HeLa cells were treated with granulysin Bid degradation was blocked, same as cytochrome c and apoptosis inducing factor (AIF) release (Zhang et al., 2009).

Stoka et al. showed that incubation of rat mitochondria to uncleaved Bid resulted only in insignificant levels of cytochrome c release, while exposure to both uncleaved Bid and lysosomal extracts resulted in cytochrome c release (Stoka et al., 2001). Other studies confirmed necessity of tBid for cytochrome c release (Gross et al., 1999; Luo et al., 1998).

Bid knockout mouse embryonic fibroblasts (MEFs) and Bax/Bak deficient MEFs were more resistant to granulysin induced death compared to wild type, and they released less cytochrome c and AIF (Zhang et al., 2009; Lindsten et al., 2000). Bcl-2-overexpressed HeLa cells almost completely blocked the release of cytochrome c and AIF after granulysin treatment (Zhang et al., 2009). Overexpression of Bcl-2 is also suppressing oxidative stress induced apoptosis (Zhao et al., 2000).

Some studies stated that certain cell types such as hepatocytes appear to require a Bid in order to disrupt mitochondrial membrane, release cytochrome c and following steps to execute apoptosis (Korsmeyer et al., 2000). They also proved that BH3 domain of tBid was not required for targeting mitochondrial membrane but it is required for cytochrome c release.

Using specific inhibitors it was demonstrated that cytosolic cathepsin D triggers Bax activation and translocation to mitochondria, resulting release of AIF from mitochondria, and the apoptosis (Bidere et al., 2003).

Incubation of cleaved Bid with mitochondria promotes oligomerization of membrane bound Bak and cytochrome c release (Wei et al., 2000).

Bax/Bak double knockout MEFs didn't show MMP induced by ciprofloxacin, norfloxacin and hydroxychloroquine, while increased LMP was detected (Boya et al., 2003).

Incubation of Bax with isolated mitochondria resulted in cytochrome c release while Bcl-xl inhibits this release (Jurgensmeier et al., 1998)

The length of the core dimer of Bax or Bak is the approximate width of the mitochondrial outer membrane, and the bend observed in the structures may be accommodated by the curved edge of the pore (Uren et al., 2017).

Uncertainties and Inconsistencies


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).

Quantitative Understanding of the Linkage


Response-response Relationship




Known modulating factors


Known Feedforward/Feedback loops influencing this KER


Domain of Applicability


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

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



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.