Grb2-associated regulator of Erk/MAPK (GAREM), is an adaptor protein related to the several cell growth factor receptor-signaling. The GAREM family has two subtypes, GAREM1 and GAREM2, both encoded in the human and mouse genome. Recent genome-wide research identified GAREM2 as a candidate of neurodegenerative diseases. Here, we use knockout (KO) mice to show the role of GAREM2, that is highly expressed in the brain. According to the comprehensive behavioral battery, they exhibited less anxiety both in elevated plus maze and open field tests, mildly increased social approaching behavior in the reciprocal social interaction test, and longer latency to immobility in the tail suspension test as compared to wild-type (WT). Additionally, the extension of neurites in the primary cultured neurons was suppressed in ones derived from GAREM2 KO mice. Furthermore, we also identified Intersectin, as a binding partner of GAREM2 in this study. Intersectin is also a multi-domain adaptor protein that regulates endocytosis and cell signaling, which can potentially alter the subcellular localization of GAREM2. The important molecules, such as the neurotrophin receptor and Erk family, that are involved in the signaling pathway of the neural cell growth in the mouse brain, have been reported to participate in emotional behavior. As GAREM plays a role in the cellular growth factor receptor signaling pathway, GAREM2 may have a common role related to the transduction of Erk signaling in the higher brain functions.
IgE class switch recombination (CSR) is under the tight control to maintain the low concentration of serum IgE. IL-4 and CD40 signal induces IgE CSR. NF-κB classical pathway and STAT6 was indicated in this pathway. In this study, we prepared a M12 cell line expressing TRAF3 in an inducible manner. This cell line showed impaired signal transduction of NF-κB alternative pathway and diminished expression of epsilon germ line transcription (εGLT), thus indicating NF-κB alternative pathway was involved in IgE CSR. CaMKII was activated after IL-4 and anti-CD40 Ab stimulation, and KN-93, a CaMKII inhibitor, inhibited both activation of NF-κB alternative pathway and IgE CSR. NF-κB alternative pathway is characterized by the NIK activation after TRAF3 degradation through ubiquitination. This ubiquitination of TRAF3 was enhanced by CaMKII and alpha4 in HEK293T cells. Alpha4 was phosphorylated by CaMKII, and alpha4 associated with TRAF3. CaMKII also regulated IgE CSR in normal splenic B cells induced by IL-4 and anti-CD40 Ab stimulation.
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