National Centre for Cell Science, Ganeshkhind, Pune 411 007, India.
J Immunol. 2012 Mar 1;188(5):2328-37. doi: 10.4049/jimmunol.1101678. Epub 2012 Jan 23.
Immunological homeostasis is often maintained by counteractive functions of two different cell types or two different receptors signaling through different intermediates in the same cell. One of these signaling intermediates is protein kinase C (PKC). Ten differentially regulated PKC isoforms are integral to receptor-triggered responses in different cells. So far, eight PKC isoforms are reported to be expressed in macrophages. Whether a single receptor differentially uses PKC isoforms to regulate counteractive effector functions has never been addressed. As CD40 is the only receptor characterized to trigger counteractive functions, we examined the relative role of PKC isoforms in the CD40-induced macrophage functions. We report that in BALB/c mouse macrophages, higher doses of CD40 stimulation induce optimum phosphorylation and translocation of PKCα, βI, βII, and ε whereas lower doses of CD40 stimulation activates PKCδ, ζ, and λ. Infection of macrophages with the protozoan parasite Leishmania major impairs PKCα, βI, βII, and ε isoforms but enhances PKCδ, ζ, and λ isoforms, suggesting a reciprocity among these PKC isoforms. Indeed, PKCα, βI, βII, and ε isoforms mediate CD40-induced p38MAPK phosphorylation, IL-12 expression, and Leishmania killing; PKCδ and ζ/λ mediate ERK1/2 phosphorylation, IL-10 production, and parasite growth. Treatment of the susceptible BALB/c mice with the lentivirally expressed PKCδ- or ζ-specific short hairpin RNA significantly reduces the infection and reinstates host-protective IFN-γ-dominated T cell response, defining the differential roles for PKC isoforms in immune homeostasis and novel PKC-targeted immunotherapeutic and parasite-derived immune evasion strategies.
免疫稳态通常是通过两种不同类型的细胞或两种不同的受体通过同一细胞中的不同中间产物发挥拮抗作用来维持的。其中一种信号转导中间产物是蛋白激酶 C（PKC）。十种不同调节的 PKC 同工型是不同细胞中受体触发反应的组成部分。到目前为止，据报道有八种 PKC 同工型在巨噬细胞中表达。是否单个受体通过不同的 PKC 同工型来调节拮抗效应功能，这一点尚未得到解决。由于 CD40 是唯一被表征为触发拮抗功能的受体，因此我们研究了 PKC 同工型在 CD40 诱导的巨噬细胞功能中的相对作用。我们报告说，在 BALB/c 小鼠巨噬细胞中，较高剂量的 CD40 刺激诱导 PKCα、βI、βII 和 ε 的最佳磷酸化和易位，而较低剂量的 CD40 刺激激活 PKCδ、ζ 和 λ。原虫寄生虫利什曼原虫感染巨噬细胞会削弱 PKCα、βI、βII 和 ε 同工型，但增强 PKCδ、ζ 和 λ 同工型，表明这些 PKC 同工型之间存在相互作用。事实上，PKCα、βI、βII 和 ε 同工型介导 CD40 诱导的 p38MAPK 磷酸化、IL-12 表达和利什曼原虫杀伤；PKCδ 和 ζ/λ 介导 ERK1/2 磷酸化、IL-10 产生和寄生虫生长。用慢病毒表达的 PKCδ 或 ζ 特异性短发夹 RNA 处理易感的 BALB/c 小鼠，可显著降低感染并恢复宿主保护性 IFN-γ 主导的 T 细胞反应，从而确定了 PKC 同工型在免疫稳态中的差异作用和新的 PKC 靶向免疫治疗和寄生虫衍生的免疫逃逸策略。
