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TNF‐α‐mediated neutrophil apoptosis involves Ly‐GDI, a Rho GTPase regulator
Author(s) -
Kettritz Ralph,
Xu YaXin,
Faass Bettina,
Klein Jon B.,
Müller EvaC.,
Otto Albrecht,
Busjahn Andreas,
Luft Friedrich C.,
Haller Hermann
Publication year - 2000
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.68.2.277
Subject(s) - phosphorylation , fibronectin , tyrosine phosphorylation , apoptosis , biology , tyrosine , microbiology and biotechnology , cleavage (geology) , blot , biochemistry , paleontology , fracture (geology) , extracellular matrix , gene
We investigated intracellular signaling events involved in fibronectin‐accelerated TNF‐α‐mediated PMN apoptosis by means of 2‐D gel electrophoresis and western blotting. Proteins were sequenced with electrospray ionization mass spectrometry. Apoptosis was quantitated by flow cytometry. We detected a cluster of acidic, high molecular‐weight proteins that were only tyrosine phosphorylated when TNF‐α‐treated PMN interacted with fibronectin. Sequence analysis revealed that one of these proteins was Ly‐GDI, a regulator of Rho GTPases. Fibronectin increased the TNF‐α‐induced Ly‐GDI cleavage, yielding a 23‐kD fragment. At 8 h, intact Ly‐GDI was decreased to 33% on fibronectin, compared with 69% on PolyHema ( P <0.05). Inhibition of tyrosine phosphorylation prevented phosphorylation of Ly‐GDI, fibronectin‐accelerated Ly‐GDI cleavage, and fibronectin‐accelerated apoptosis in TNF‐α‐treated PMN. We found that Ly‐GDI cleavage was dependent on caspase‐3 activation and that caspase‐3 inhibition decreased apoptosis. We conclude that tyrosine phosphorylation of Ly‐GDI, followed by increased caspase‐3‐mediated Ly‐GDI cleavage, is a signaling event associated with accelerated TNF‐α‐mediated apoptosis on fibronectin.