In endothelial cells, vascular endothelial growth factor (VEGF) induces an accumulation of stress fibers associated with new actin polymerization and rapid formation of focal adhesions at the ventral surface of the cells. This cytoskeletal reorganization results in an intense motogenic activity. Using porcine endothelial cells expressing one or the other type of the VEGF receptors, VEGFR1 or VEGFR2, or human umbilical vein endothelial cells pretreated with a VEGFR2 neutralizing antibody, we show that VEGFR2 is responsible for VEGF-induced activation of the stress-activated protein kinase-2/p38 (SAPK2/p38), phosphorylation of focal adhesion kinase (FAK), and enhanced migratory activity. Activation of SAPK2/p38 triggered actin polymerization whereas FAK, which was phosphorylated independently of SAPK2/p38, initiated assembly of focal adhesions. Both processes contributed to the formation of stress fibers. Geldanamycin, an inhibitor of HSP90 blocked tyrosine phosphorylation of FAK, assembly of focal adhesions, actin reorganization, and cell migration, all of which were reversed by overexpressing HSP90. We conclude that VEGFR2 mediates the physiological effect of VEGF on cell migration and that two independent pathways downstream of VEGFR2 regulate actin-based motility. One pathway involves SAPK2/p38 and leads to enhanced actin polymerization activity. The other involves HSP90 as a permissive signal transduction factor implicated in FAK phosphorylation and assembly of focal adhesions.

Interleukin-4 (IL-4) is an immunoregulatory cytokine produced by activated T lymphocytes to promote the growth and differentiation of cells that participate in immune defense. This study demonstrates the rapid activation of a specific DNA binding factor by IL-4. The IL-4 nuclear-activated factor (IL-4 NAF) appeared within minutes of IL-4 stimulation and recognized a specific DNA sequence found in the promoters of IL-4-responsive genes. Activation of this putative transcription factor required tyrosine phosphorylation, and antibodies specific for phosphotyrosine recognize the IL-4 NAF-DNA complex. Thus, IL-4 appears to transduce a signal to the nucleus through tyrosine phosphorylation of a latent DNA binding factor.

Article abstract-We reviewed the clinical findings in 55 patients with cerebellar degeneration associated with the anti-Yo antibody (an anti-Purkinje cell antibody identified in this study by histochemistry and Western blot). The patients were all women, 26 to 85 years old. Fifty-two of them proved to have malignancies, almost exclusively breast or gynecologic cancers and usually confined to the involved organs and local lymph nodes. One woman had adenocarcinoma of the lung, and in three no malignancy has yet been identified. In 34 of 52 patients with cancer, the neurologic syndrome preceded the diagnosis of cancer and in many led to that diagnosis. Patients subacutely developed a pancerebellar disorder that was substantially disabling in most, with 37 of 48 assessable patients being unable to walk or sit unassisted. Laboratory evaluation revealed lymphocytic pleocytosis in 35 patients, with eventual cerebellar atrophy on imaging studies in seventeen. The disabling neurologic syndrome generally did not respond to treatment, but the cancer was often successfully treated. The presence of the anti-Yo antibody in patients with cerebellar symptoms warrants an aggressive approach to diagnosis and treatment of the underlying cancer, as many are curable at the time neurologic symptoms develop.

Cytokines function as protein mediators that play a critical role in host defense and serve as a communication link between cells of native and acquired immunity. Cells respond to cytokines with specific biological changes that are dependent on the activation of new gene expression. Studies of the mechanism by which signals are mediated from the receptor to the nucleus by the interferon cytokines have revealed the activation by tyrosine phosphorylation of latent cytoplasmic transcription factors that subsequently translocate to the nucleus (1-4). This pathway has served as a model for signal transmission by many other cytokines including interleukin-4 (IL-4).