Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

The dual specific kinase SAPK/ERK1 kinase (SEK1; mitogen-activated protein kinase kinase 4/Jun NH2 terminal kinase [ JNK] kinase) is a direct activator of stress-activated protein kinases ([SAPKs]/JNKs) in response to CD28 costimulation, CD40 signaling, or activation of the germinal center kinase. Here we show that SEK1−/− recombination-activating gene (RAG)2−/− chimeric mice have a partial block in B cell maturation. However, peripheral B cells displayed normal responses to IL-4, IgM, and CD40 cross-linking. SEK1−/− peripheral T cells showed decreased proliferation and IL-2 production after CD28 costimulation and PMA/Ca2+ ionophore activation. Although CD28 expression was absolutely crucial to generate vesicular stomatitis virus (VSV)-specific germinal centers, SEK1−/−RAG2−/− chimeras mounted a protective antiviral B cell response, exhibited normal IgG class switching, and made germinal centers in response to VSV. Interestingly, PMA/Ca2+ ionophore stimulation, which mimics TCR–CD3 and CD28-mediated signal transduction, induced SAPK/JNK activation in peripheral T cells, but not in thymocytes, from SEK1−/− mice. These results show that signaling pathways for SAPK activation are developmentally regulated in T cells. Although SEK1−/− thymocytes failed to induce SAPK/JNK in response to PMA/Ca2+ ionophore, SEK1−/−RAG2−/− thymocytes proliferated and made IL-2 after PMA/Ca2+ ionophore and CD3/CD28 stimulation, albeit at significantly lower levels compared to SEK1+/+RAG2−/− thymocytes, implying that CD28 costimulation and PMA/Ca2+ ionophore–triggered signaling pathways exist that can mediate proliferation and IL-2 production independently of SAPK activation. Our data provide the first genetic evidence that SEK1 is an important effector molecule that relays CD28 signaling to IL-2 production and T cell proliferation.

Original publication

DOI

10.1084/jem.186.6.941

Type

Journal article

Journal

Journal of Experimental Medicine

Publisher

Rockefeller University Press

Publication Date

15/09/1997

Volume

186

Pages

941 - 953