The CrkL adapter protein is required for type I interferon-dependent gene transcription and activation of the small G-protein Rap1.

We sought to determine the functional role of the CrkL adapter protein and downstream pathways in interferon signaling. In experiments using CrkL(--) mouse embryonic fibroblasts, we found that CrkL is required for IFN alpha-dependent gene transcription via GAS elements, apparently via the formation of DNA-binding complexes with Stat5. On the other hand, gene transcription via ISRE elements is intact in the absence of CrkL, indicating that the regulatory effects on gene transcription are mediated only via the formation of CrkL:Stat5 complexes. Our studies also indicate that activation of the small GTPase Rap1 by IFN alpha is defective in cells lacking CrkL, indicating that the protein plays a critical role in regulating activation of the growth inhibitory C3G/Rap1 pathway. The IFN alpha-inducible activation of the small GTPase Rap1 requires a functional N-terminus SH3 domain in the CrkL protein, while the C-terminus SH3 domain does not appear to play a role in such a CrkL-function. We also demonstrate that both the Tyk-2 and Jak-1 kinases are required for activation of the CrkL/Rap1 pathway, as the Type I IFN-dependent GTP-bound form of Rap1 is inhibited by overexpression of dominant-negative Tyk-2 or Jak-1 mutants and is defective in cells lacking Tyk-2 or Jak-1. Taken altogether, these findings indicate that CrkL provides an important link between Jak-kinases and downstream cascades that play critical roles in IFN-dependent transcriptional regulation and induction of growth inhibitory responses.

[1]  B. Druker,et al.  Mice lacking the homologue of the human 22q11.2 gene CRKL phenocopy neurocristopathies of DiGeorge syndrome , 2001, Nature Genetics.

[2]  L. Platanias,et al.  Engagement of the CrkL adaptor in interferon α signalling in BCR–ABL‐expressing cells , 2001 .

[3]  A. Miyajima,et al.  Thrombopoietin and interleukin-2 induce association of CRK with STAT5. , 2000, Biochemical and biophysical research communications.

[4]  L. Platanias,et al.  Engagement of the CrkL Adapter in Interleukin-5 Signaling in Eosinophils* , 2000, The Journal of Biological Chemistry.

[5]  L. Platanias,et al.  The Rac1/p38 mitogen-activated protein kinase pathway is required for interferon alpha-dependent transcriptional activation but not serine phosphorylation of Stat proteins. , 2000, The Journal of biological chemistry.

[6]  M. Ballmaier,et al.  Thrombopoietin induces the generation of distinct Stat1, Stat3, Stat5a and Stat5b homo- and heterodimeric complexes with different kinetics in human platelets. , 2000, Experimental hematology.

[7]  B. Druker,et al.  CrkL functions as a nuclear adaptor and transcriptional activator in Bcr-Abl-expressing cells. , 2000, Experimental hematology.

[8]  L. Platanias,et al.  IFN-γ Activates the C3G/Rap1 Signaling Pathway1 , 2000, The Journal of Immunology.

[9]  L. Platanias,et al.  Signaling pathways activated by interferons. , 1999, Experimental hematology.

[10]  L. Platanias,et al.  Activation of the p 38 Mitogen-activated Protein Kinase by Type I Interferons , 1999 .

[11]  N. Miyasaka,et al.  CrkL Mediates Ras-dependent Activation of the Raf/ERK Pathway through the Guanine Nucleotide Exchange Factor C3G in Hematopoietic Cells Stimulated with Erythropoietin or Interleukin-3* , 1999, The Journal of Biological Chemistry.

[12]  B. Williams,et al.  p38 MAP kinase is required for STAT1 serine phosphorylation and transcriptional activation induced by interferons , 1999, The EMBO journal.

[13]  D. J. Van Den Berg,et al.  CrkL and CrkII participate in the generation of the growth inhibitory effects of interferons on primary hematopoietic progenitors. , 1999, Experimental hematology.

[14]  L. Platanias,et al.  Activation of a CrkL-Stat5 Signaling Complex by Type I Interferons* , 1999, The Journal of Biological Chemistry.

[15]  G. Stark,et al.  How cells respond to interferons. , 1998, Annual review of biochemistry.

[16]  B. Druker,et al.  Erythropoietin Induces Tyrosine Phosphorylation of Jak2, STAT5A, and STAT5B in Primary Cultured Human Erythroid Precursors , 1998 .

[17]  L. Platanias,et al.  The Type I Interferon Receptor Mediates Tyrosine Phosphorylation of the CrkL Adaptor Protein* , 1997, The Journal of Biological Chemistry.

[18]  G. Freeman,et al.  Maintenance of human T cell anergy: blocking of IL-2 gene transcription by activated Rap1. , 1997, Science.

[19]  M. White,et al.  The IRS-pathway operates distinctively from the Stat-pathway in hematopoietic cells and transduces common and distinct signals during engagement of the insulin or interferon-alpha receptors. , 1997, Blood.

[20]  R. Pine,et al.  Kinase-deficient forms of Jak1 and Tyk2 inhibit interferon alpha signaling in a dominant manner. , 1997, European journal of biochemistry.

[21]  M. White,et al.  Activation of the phosphatidylinositol 3-kinase serine kinase by IFN-alpha. , 1997, Journal of immunology.

[22]  R. Salgia,et al.  The BCR/ABL oncogene alters interaction of the adapter proteins CRKL and CRK with cellular proteins , 1997, Leukemia.

[23]  M. White,et al.  The Type I Interferon Receptor Mediates Tyrosine Phosphorylation of Insulin Receptor Substrate 2 (*) , 1996, The Journal of Biological Chemistry.

[24]  A. Saïb,et al.  Transcriptional induction of the PML growth suppressor gene by interferons is mediated through an ISRE and a GAS element. , 1995, Oncogene.

[25]  M. White,et al.  Interferon-α Engages the Insulin Receptor Substrate-1 to Associate with the Phosphatidylinositol 3′-Kinase (*) , 1995, The Journal of Biological Chemistry.

[26]  B. Druker,et al.  Crkl is the major tyrosine-phosphorylated protein in neutrophils from patients with chronic myelogenous leukemia. , 1994, The Journal of biological chemistry.

[27]  J. Darnell,et al.  Jak-STAT pathways and transcriptional activation in response to IFNs and other extracellular signaling proteins. , 1994, Science.

[28]  S. Cook,et al.  RapV12 antagonizes Ras‐dependent activation of ERK1 and ERK2 by LPA and EGF in Rat‐1 fibroblasts. , 1993, The EMBO journal.

[29]  H. Kitayama,et al.  A ras-related gene with transformation suppressor activity , 1989, Cell.

[30]  B. Mayer,et al.  A novel viral oncogene with structural similarity to phospholipase C , 1988, Nature.

[31]  K C Zoon,et al.  Interferons and their actions. , 1987, Annual review of biochemistry.