Loss of tau and Fyn reduces compensatory effects of MAP2 for tau and reveals a Fyn-independent effect of tau on calcium.

Microtubule-associated protein tau associates with Src family tyrosine kinase Fyn and is tyrosine phosphorylated by Fyn. The presence of tyrosine phosphorylated tau in AD and the involvement of Fyn in AD has drawn attention to the tau-Fyn complex. In this study, a tau-Fyn double knockout (DKO) mouse was generated to investigate the role of the complex. DKO mice resembled Fyn KO in novel object recognition and contextual fear conditioning tasks and resembled tau KO mice in the pole test and protection from pentylenetetrazole-induced seizures. In glutamate-induced Ca2+ response, Fyn KO was decreased relative to WT and DKO had a greater reduction relative to Fyn KO, suggesting that tau may have a Fyn-independent role. Since tau KO resembled WT in its Ca2+ response, we investigated whether microtubule-associated protein 2 (MAP2) served to compensate for tau, since the MAP2 level was increased in tau KO but decreased in DKO mice. We found that like tau, MAP2 increased Fyn activity. Moreover, tau KO neurons had increased density of dendritic MAP2-Fyn complexes relative to WT neurons. Therefore, we hypothesize that in the tau KO, the absence of tau would be compensated by MAP2, especially in the dendrites, where tau-Fyn complexes are of critical importance. In the DKO, decreased levels of MAP2 made compensation more difficult, thus revealing the effect of tau in the Ca2+ response.

Tau interacts with SHP2 in neuronal systems and in Alzheimer's disease brains.

Microtubule-associated protein tau, an integral component of neurofibrillary tangles, interacts with a variety of signaling molecules. Previously, our laboratory reported that nerve growth factor (NGF)-induced MAPK activation in a PC12-derived cell line was potentiated by tau, with phosphorylation at T231 being required. Therefore, we sought to identify a signaling molecule involved in the NGF-induced Ras-MAPK pathway that interacted with phospho-T231-tau. Here, we report that the protein tyrosine phosphatase SHP2 (also known as PTPN11) interacted with tau, with phospho-T231 significantly enhancing the interaction. By using proximity ligation assays, we found that endogenous tau-SHP2 complexes were present in neuronal cells, where the number of tau-SHP2 complexes significantly increased when the cells were treated with NGF, with phosphorylation at T231 being required for the increase. The interaction did not require microtubule association, and an association between tau and activated SHP2 was also found. Tau-SHP2 complexes were also found in both primary mouse hippocampal cultures and adult mouse brain. Finally, SHP2 levels were upregulated in samples from patients with mild and severe Alzheimer's disease (AD), and the level of tau-SHP2 complexes were increased in AD patient samples. These findings strongly suggest a role for the tau-SHP2 interaction in NGF-stimulated neuronal development and in AD.This article has an associated First Person interview with the first author of the paper.

Obesity alters immune and metabolic profiles: New insight from obese-resistant mice on high-fat diet.

OBJECTIVE: Diet-induced obesity has been shown to alter immune function in mice, but distinguishing the effects of obesity from changes in diet composition is complicated. It was hypothesized that immunological differences would exist between diet-induced obese (DIO) and obese-resistant (OB-Res) mice fed the same high-fat diet (HFD). METHODS: BALB/c mice were fed either standard chow or HFD to generate lean or DIO and OB-Res mice, respectively. Resulting mice were analyzed for serum immunologic and metabolic profiles and cellular immune parameters. RESULTS: BALB/c mice on HFD were categorized as DIO or OB-Res, based on body weight versus lean controls. DIO mice were physiologically distinct from OB-Res mice, whose serum insulin, leptin, gastric inhibitory polypeptide, and eotaxin concentrations remained similar to lean controls. DIO mice had increased macrophage(+) crown-like structures in white adipose tissue, although macrophage percentages were unchanged from OB-Res and lean mice. DIO mice also had decreased splenic CD4(+) T cells, elevated serum GM-CSF, and increased splenic CD11c(+) dendritic cells, but impaired dendritic cell stimulatory capacity (P < 0.05 vs. lean controls). These parameters were unaltered in OB-Res mice versus lean controls. CONCLUSIONS: Diet-induced obesity results in alterations in immune and metabolic profiles that are distinct from effects caused by HFD alone.

A therapeutic microparticle-based tumor lysate vaccine reduces spontaneous metastases in murine breast cancer.

Metastatic breast cancer is currently incurable, and available therapies are associated with severe toxicities. Induction of protective anti-tumor immunity is a promising therapeutic approach for disseminated breast cancer, as immune responses are (i) systemic; (ii) antigen-specific; and (iii) capable of generating long-lived "memory" populations that protect against future tumor recurrences. Pursuant with this approach, we have developed a novel heterologous prime/boost vaccination regimen that reduces spontaneous lung metastases in mice with established murine 4T1 adenocarcinoma breast tumors. In our studies, mice were orthotopically challenged with luciferase-expressing 4T1 tumor cells; luciferase expression was retained in vivo, enabling us to quantitatively track metastatic tumor growth via bioluminescent imaging. On day 6 post-challenge, mice received a therapeutic "prime" consisting of bulk tumor lysates encapsulated in poly(lactic-co-glycolic) acid (PLGA) microparticles (MPs). On day 11, mice received a "boost" composed of free tumor lysates plus a cocktail of Toll-like receptor (TLR)-stimulating adjuvants. Tumor progression was monitored in vaccinated and untreated mice for 25 days, a time at which 100% of untreated mice had detectable lung tumors. PLGA MPs injected subcutaneously trafficked to draining lymph nodes and were efficiently phagocytosed by dendritic cells (DCs) within 48 h. Our combination therapy reduced metastatic lung tumor burdens by 42% and did not induce autoimmunity. These findings illustrate that vaccines based upon MP delivery of tumor lysates can form the basis of an effective treatment for metastatic breast cancer and suggest that similar approaches may be both efficacious and well-tolerated in the clinic.