Ionizing Radiation Stimulates a Grb2-mediated Association of the Stress-activated Protein Kinase with Phosphatidylinositol 3-Kinase

Abstract

The stress-activated protein (SAP) kinases are induced by tumor necrosis factor, oncoproteins, and UV light. The present studies demonstrate that ionizing radiation (IR) activates p54 SAP kinase. IR-induced activation of SAP kinase is associated with binding to the SH2/SH3-containing adaptor protein Grb2. This interaction is mediated by the SH3 domains of Grb2 and the proline-rich sequence PPPKIP in the carboxy-terminal region of SAP kinase. We also demonstrated that SAP kinase and the p85 alpha-subunit of phosphatidylinositol (PI) 3-kinase form a complex in irradiated cells. The results indicate that this complex involves binding of the p85 alpha subunit of PI 3-kinase to the SH2 domain of Grb2. The functional role of linking SAP kinase to PI 3-kinase is further supported by the finding that wortmannin, an inhibitor of PI 3-kinase, stimulates SAP kinase activity. These results suggest that the cellular response to IR may include regulation of SAP kinase by a PI 3-kinase-dependent signaling pathway.

Induction of apoptosis in U937 human leukemia cells by suberoylanilide hydroxamic acid (SAHA) proceeds through pathways that are regulated by Bcl-2/Bcl-XL, c-Jun, and p21CIP1, but independent of p53

“…Values represent the means+s.d. for a representative experiment; two additional studies yielded equivalent results (Franklin and Kraft, 1995) as well as MAPK-related (Kharbanda et al, 1994) signaling pathways. Furthermore, pharmacologic blockade of the MEK/ERK module (by PD98059) or interruption of the SAPK-JNK/AP-1 pathway (by TAM67) interferes with retinoic acid-and PMA-related actions respectively (Yen et al, 1998;Dong et al, 1997).…”

“…SAHA-mediated apoptosis is partially dependent upon an intact SAPK-JNK and c-Jun/AP1 pathway, but is independent of MEK/MAPK Leukemic cell maturation has been linked to activation of c-Jun and the AP1 transcription factor (Franklin and Kraft., 1995) as well as mitogen-activated protein kinase (MAPK) (Kharbanda et al, 1994). To assess the e ects of SAHA on these pathways, expression of the phosphorylated forms of stress-activated protein kinase (SAPK) and MAPK was monitored.…”

BCL-6 is phosphorylated at multiple sites in its serine- and proline-clustered region by mitogen-activated protein kinase (MAPK) in vivo

“…It was reported that MAPK is activated during TPAinduced monocytic lineage di erentiation in HL-60 cells (Kharbanda et al, 1994). Meanwhile, we found recently that the expression of the BCL-6 gene is induced during monocytic lineage di erentiation in TPA-treated HL-60 and U-937 cells (Yamochi et al, in press).…”

“…MAPK has been shown to be involved in a broad spectrum of cellular events, including cell growth (Gotoh et al, 1991a, b;Pages et al, 1993;Mansour et al, 1994), di erentiation and maturation (Kosako et al, 1994;Cowley et al, 1994;Kharbanda et al, 1994). It was reported that MAPK is activated during TPAinduced monocytic lineage di erentiation in HL-60 cells (Kharbanda et al, 1994).…”

Expression of the antiapoptotic MCL1 gene product is regulated by a mitogen activated protein kinase-mediated pathway triggered through microtubule disruption and protein kinase C

“…In a variety of cell types including myeloid cells, exposure to TPA results in the activation of PKC and subsequently in the phosphorylation and activation of the MAP kinases ERK1 and -2 (Kharbanda et al, 1994;Kolch et al, 1993). It therefore seemed likely that exposure to TPA, and possibly also the microtubule-disrupting agents, might result in an increase in ERK phosphorylation in ML-1 cells.…”