The tyrosine kinase Lck is required for CD95-independent caspase-8 activation and apoptosis in response to ionizing radiation

• Induction of apoptosis is a hallmark of cytostatic drug and radiation-induced cell death in human lymphocytes and lymphoma cells. However, the mechanisms leading to apoptosis are not well understood. We provide evidence that ionizing radiation induces a rapid activation of caspase-8 (FLICE) followed by apoptosis independently of CD95 ligand/receptor interaction. The radiation induced cleavage pattern of procaspase-8 into mature caspase-8 resembled that following CD95 crosslinking and resulted in cleavage of the proapoptotic substrate BID. Overexpression of dominant-negative caspase-8 interfered with radiation-induced apoptosis, Caspase-8 activation by ionizing radiation was not observed in cells genetically defective for the Src-like tyrosine kinase Lck, Cells lacking Lck also displayed a marked resistance towards apoptosis induction upon ionizing radiation. After retransfection of Lck, caspase-8 activation and the capability to undergo apoptosis in response to ionizing radiation was restored. We conclude that radiation activates caspase-8 via an Lck-controlled pathway independently of CD95 ligand expression, This is a novel signaling event required for radiation induced apoptosis in T lymphoma cells.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Cancer och onkologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Cancer and Oncology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

Apoptosis

b-cells

caspase-8/FLICE

cytochrome-c

death

drug-induced apoptosis

fas-induced apoptosis

Lck

leukemia-cells

ligand expression

lymphoma

phosphorylation

sh2 domain

t-cells

tyrosine kinase

Publikations- och innehållstyp

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