Overcoming drug resistance remains a key challenge to cure patients with acute and chronic B cell malignancies. Here, we describe a stromal cell–autonomous signaling pathway, which contributes to drug resistance of malignant B cells. We show that protein kinase C (PKC)–β–dependent signals from bone marrow–derived stromal cells markedly decrease the efficacy of cytotoxic therapies. Conversely, small-molecule PKC-β inhibitors antagonize prosurvival signals from stromal cells and sensitize tumor cells to targeted and nontargeted chemotherapy, resulting in enhanced cytotoxicity and prolonged survival in vivo. Mechanistically, stromal PKC-β controls the expression of adhesion and matrix proteins, required for activation of phosphoinositide 3-kinases (PI3Ks) and the extracellular signal–regulated kinase (ERK)–mediated stabilization of B cell lymphoma–extra large (BCL-X_L) in tumor cells. Central to the stroma-mediated drug resistance is the PKC-β–dependent activation of transcription factor EB, regulating lysosome biogenesis and plasma membrane integrity. Stroma-directed therapies, enabled by direct inhibition of PKC-β, enhance the effectiveness of many antileukemic therapies.

In healthy hosts, acute infection with the opportunistic pathogen Toxoplasma gondii is controlled by innate production of IL-12, a key cytokine crucial for the development of protective immunity. Previous work has established that the mitogen-activated protein kinases (MAPK), particularly p38 and ERK1/2, are important regulators of T. gondii-induced IL-12 synthesis. Here we report that host cell Ca2+ is required for activation of MAPK by T. gondii, as well as LPS and CpG, and for parasite-induced synthesis of IL-12. In addition, pharmacological mobilization of Ca2+ stores in macrophages treated with parasites or LPS enhanced MAPK phosphorylation initiated by these stimuli. Investigation of the upstream mechanism by which Ca2+ regulates MAPK activation revealed that T. gondii induced acute activation of conventional, Ca2+-dependent PKCα and PKCβ, which are required for infection-induced MAPK activation and production of IL-12. Despite these findings, neither acute parasite infection nor LPS initiated a measurable Ca2+ response in macrophages, suggesting that low levels of Ca2+ are permissive for initiation of pro-inflammatory signaling. Together these data identify host cell Ca2+ and PKC as crucial regulators of the innate immune response to microbial stimuli, including T. gondii.

Background. The integrity of the intestinal epithelium is critical for the absorption and retention of fluid and nutrients. The intestinal epithelium al

Exercise-induced phosphorylation of FXYD1 is a potential important regulator of Na⁺-K⁺-pump activity. It was investigated whether skeletal muscle contractions induce phosphorylation of FXYD1 and whether protein kinase Cα (PKCα) activity is a prerequisite for this possible mechanism. In part 1, human muscle biopsies were obtained at rest, after 30 s of high-intensity exercise (166 ± 31% of V̇o_2max) and after a subsequent 20 min of moderate-intensity exercise (79 ± 8% of V̇o_2max). In general, FXYD1 phosphorylation was increased compared with rest both after 30 s ( P < 0.05) and 20 min ( P < 0.001), and more so after 20 min compared with 30 s ( P < 0.05). Specifically, FXYD1 ser63, ser68, and combined ser68 and thr69 phosphorylation were 26–45% higher ( P < 0.05) after 20 min of exercise than at rest. In part 2, FXYD1 phosphorylation was investigated in electrically stimulated soleus and EDL muscles from PKCα knockout (KO) and wild-type (WT) mice. Contractile activity caused FXYD1 ser68 phosphorylation to be increased ( P < 0.001) in WT soleus muscles but to be reduced ( P < 0.001) in WT extensor digitorum longus. In contrast, contractile activity did not affect FXYD1 ser68 phosphorylation in the KO mice. In conclusion, exercise induces FXYD1 phosphorylation at multiple sites in human skeletal muscle. In mouse muscles, contraction-induced changes in FXYD1 ser68 phosphorylation are fiber-type specific and dependent on PKCα activity.

Protein kinase C iota (PKCι) functions as a bonafide human oncogene in lung and ovarian cancer and is required for Kras^G12D-mediated lung cancer initiation and progression. PKCι expression is required for pancreatic cancer cell growth and maintenance of the transformed phenotype; however, nothing is known about the role of PKCι in pancreas development or pancreatic tumorigenesis. In this study, we investigated the effect of pancreas-specific ablation of PKCι expression on pancreatic cellular homeostasis, susceptibility to pancreatitis, and Kras^G12D-mediated pancreatic cancer development. Knockout of pancreatic Prkci significantly increased pancreatic immune cell infiltration, acinar cell DNA damage, and apoptosis, but reduced sensitivity to caerulein-induced pancreatitis. Prkci-ablated pancreatic acinar cells exhibited P62 aggregation and a loss of autophagic vesicles. Loss of pancreatic Prkci promoted Kras^G12D-mediated pancreatic intraepithelial neoplasia formation but blocked progression to adenocarcinoma, consistent with disruption of autophagy. Our results reveal a novel promotive role for PKCι in pancreatic epithelial cell autophagy and pancreatic cancer progression.

Background: The homeobox containing transcription factor Uncx4.1 is, amongst others, expressed in the mouse midbrain. The early expression of this transcription factor in the mouse, as well as in the chick midbrain, points to a conserved function of Uncx4.1, but so far a functional analysis in this brain territory is missing. The goal of the current study was to analyze in which midbrain neuronal subgroups Uncx4.1 is expressed and to examine whether this factor plays a role in the early development of these neuronal subgroups. Results: We have shown that Uncx4.1 is expressed in GABAergic, glutamatergic and dopaminergic neurons in the mouse midbrain. In midbrain dopaminergic (mDA) neurons Uncx4.1 expression is particularly high around E11.5 and strongly diminished already at E17.5. The analysis of knockout mice revealed that the loss of Uncx4.1 is accompanied with a 25% decrease in the population of mDA neurons, as marked by tyrosine hydroxylase (TH), dopamine transporter (DAT), Pitx3 and Ngn2. In contrast, the number of glutamatergic Pax6-positive cells was augmented, while the GABAergic neuron population appears not affected in Uncx4.1-deficient embryos. Conclusion: We conclude that Uncx4.1 is implicated in the development of mDA neurons where it displays a unique temporal expression profile in the early postmitotic stage. Our data indicate that the mechanism underlying the role of Uncx4.1 in mDA development is likely related to differentiation processes in postmitotic stages, and where Ngn2 is engaged. Moreover, Uncx4.1 might play an important role during glutamatergic neuronal differentiation in the mouse midbrain.