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Hyperosmolarity triggers CD95 membrane trafficking and sensitizes rat hepatocytes toward CD95L‐induced apoptosis
Author(s) -
Reinehr Roland,
Graf Dirk,
Fischer Richard,
Schliess Freimut,
Häussinger Dieter
Publication year - 2002
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1053/jhep.2002.35447
Subject(s) - microbiology and biotechnology , fas receptor , apoptosis , protein kinase a , kinase , biology , chemistry , programmed cell death , biochemistry
The effect of hyperosmolarity on CD95 membrane targeting and CD95 ligand (CD95L)–induced apoptosis was studied in rat hepatocytes. CD95 showed a predominant intracellular localization in normoosmotically exposed rat hepatocytes, whereas hyperosmotic exposure induced, within 1 hour, CD95 trafficking to the plasma membrane followed by activation of caspase‐3 and ‐8. Hyperosmotic CD95 membrane targeting was sensitive to inhibition of c‐Jun‐N‐terminal kinase (JNK), protein kinase C (PKC), and cyclic adenosine monophosphate, but not to inhibition of extracellular regulated kinases (Erks) or p38 mitogen activated protein kinase (p38 MAPK ). Hyperosmotic CD95 targeting to the plasma membrane was dose‐dependently diminished by glutamine or taurine, probably caused by an augmentation of volume regulatory increase. Despite CD95 trafficking to the plasma membrane and caspase activation, hyperosmolarity per se did not induce apoptosis. Hyperosmolarity, however, sensitized hepatocytes toward CD95L‐induced apoptosis, as assessed by annexin V staining and terminal deoxynucleotidyl transferase‐mediated X‐dUTP nick‐end labeling (TUNEL) assay. This sensitization was abolished when hyperosmotic CD95 membrane trafficking was prevented by cyclic adenosine monophosphate, PKC, or JNK inhibition, whereas these effectors had no effect on CD95L‐induced apoptosis in normoosmotically exposed hepatocytes. CD95L addition under normoosmotic conditions caused CD95 membrane trafficking, which was sensitive to JNK inhibition, but not to cyclic adenosine monophosphate or inhibition of PKC, Erks, and p38 MAPK . In conclusion, multiple signaling pathways are involved in CD95 membrane trafficking. Hyperosmotic hepatocyte shrinkage induces CD95 trafficking to the plasma membrane, which involves JNK‐, PKA‐, and PKC‐dependent mechanisms and sensitizes hepatocytes toward CD95L‐mediated apoptosis.