Ndfip1 protein promotes the function of itch ubiquitin ligase to prevent T cell activation and T helper 2 cell-mediated inflammation

Abstract

Nedd4 family interacting protein-1 (Ndfip1) is a protein whose only known function is that it binds Nedd4, a HECT-type E3 ubiquitin ligase. Here we show that mice lacking Ndfip1 developed severe inflammation of the skin and lung and died prematurely. This condition was due to a defect in Ndfip1(-/-) T cells. Ndfip1(-/-) T cells were activated, and they proliferated and adopted a T helper 2 (Th2) phenotype more readily than did their Ndfip1(+/+) counterparts. This phenotype resembled that of Itchy mutant mice, suggesting that Ndfip1 might affect the function of Itch, an E3 ubiquitin ligase. We show that T cell activation promoted both Ndfip1 expression and its association with Itch. In the absence of Ndfip1, JunB half-life was prolonged after T cell activation. Thus, in the absence of Ndfip1, Itch is inactive and JunB accumulates. As a result, T cells produce Th2 cytokines and promote Th2-mediated inflammatory disease.

Figure 1

The Generation of Mice Homozygous for a Disrupted Ndfip1 Gene (A) The location of the gene trap vector within the Ndfip1 locus is shown. The Ndfip1 locus contains 8 exons spanning about 45 Kb of genomic DNA. (B) The gene trap vector was inserted into the second intron and results in the production of a truncated Ndfip1 mRNA that encodes exons 1 and 2. (C) Offspring resulting from the intercross between Ndfip1^+/− mice were tested by PCR to identify Ndfip1^−/− animals via the primer pairs shown in Figure 1A. (D) To confirm the disruption of Ndfip1, RNA was isolated from Ndfip1^+/+ and Ndfip1^−/− mice and RT-PCR was performed. We detect the presence of two transcripts in Ndfip1^−/− tissues, Ndfip1-AST and Ex2-βGEO. GADPH is shown as a reverse transcriptase and loading control.

Figure 2

Loss of Ndfip1 Leads to Inflammatory Disease, Splenomegally, Hepatomegally, and Extramedullary Hematopoiesis of the Spleen and Liver (A–D) H&E-stained tissue sections from 8-week-old Ndfip1^−/− ear (A), liver (B and C), and spleen (D). (E) PAS-stained sections of Ndfip1^−/− lung. (F) The number of live Ndfip1^−/− and Ndfip1^+/+ mice was measured over time.

Figure 3

Reconstitution of Wild-Type Mice with Ndfip1^−/− Marrow Leads to Inflammatory Disease C57BL6 mice were lethally irradiated and then reconstituted with Ndfip1^−/− bone marrow cells. The resulting mice developed skin lesions between 6 and 8 weeks of age. (A) The skin lesions showed an infiltration of inflammatory cells. (B and C) Histological findings in spleen (B) and liver (C) were similar to those seen in Ndfip1^−/− mice. a, inflammation; b, extramedullary hematopoiesis.

Figure 4

Mixed Bone Marrow Chimeras Reveal a Profound Defect in Ndfip1^−/− T Cells C57BL/6 mice were lethally irradiated and reconstituted with a mixture of equal numbers of Ndfip1^−/− and Ndfip1^+/+ (GFP-expressing) bone marrow. Primary and secondary lymphoid organs of the resulting mice were analyzed 5–6 weeks after the bone marrow transfer. Cells were sorted based on whether or not they expressed GFP, stained, and then treated with saponin to allow release of GFP from the cells. (A) Cells were isolated from the thymus and stained for CD4 and CD8 single-positive populations. (B) Cells from the bone marrow were stained for B cell markers (B220 and IgM) or myeloid markers (GR1). (C) Cells were isolated from the spleen and stained for B cell (B220), dendritic cell (CD11b and CD11c), or myeloid (GR1 and F4/80) markers or for markers indicating activation (CD69). (D) Spleen cells were stained for T cell-specific markers (CD4 and CD8) or markers indicating activation status (CD62L and CD44). (E) The percent of activated cells among the different populations in both the spleen and lymph nodes were quantified. Open bars represent Ndfip1^+/+ T cells, whereas the black bars represent Ndfip1^−/− T cells. Error bars depict standard errors (n = 8). Both CD4⁺ and CD8⁺ T cells lacking Ndfip1 were significantly more likely to show an activated phenotype. *p < 0.05; **p < 0.01 (paired t test).

Figure 5

T Cells Lacking Ndfip1 Are More Likely to Proliferate and Produce Th2 Cytokines (A) Spleen cells from mixed chimeras, 5–6 weeks posttransfer, were sorted based on GFP expression, labeled with CFSE, and stimulated with anti-CD3 (plate-bound) and anti-CD28, or left unstimulated. After 3 days, cells were stained, treated with saponin, and analyzed for loss of CFSE. (B) Spleen and lymph node cells from 5- to 6-week-old Ndfip1^−/− and Ndfip1^+/+ mice were isolated and depleted of CD44⁺ cells and CD8⁺ cells. Cells were then stimulated with anti-CD3 and anti-CD28 or stimulated in the presence of Th1 or Th2 differentiating conditions. The percentages represent cytokine-producing cells as a percent of the total CD4⁺ cells. Data compiled from three independent experiments show that the percent of IL-4 producers averaged 39.8% ± 5.5% for Ndfip1^+/+ and 72.9% ± 8.1% for Ndfip1^−/− T cells; p < 0.04 paired Student’s t test. IFN-γ production was not statistically different between the two genotypes.

Figure 6

Immunization of Ndfip1^−/− Mice with OVA+CFA or OVA+ALUM Leads to IL-4 Production and Increased Antigen-Specific IgE Ndfip1^+/+ and Ndfip1^−/− bone marrow chimeras were immunized with OVA+CFA or OVA+ALUM 5 weeks after reconstitution. (A) 8 days later, cells were isolated from spleens and lymph nodes and cultured in media alone or in the presence of OVA peptide (OVA323-339). Effector CD4⁺ T cells (CD4⁺, CD44^hi, CD62L^lo) were then analyzed for intracellular IL-4 or IFN-γ. (B) Sera were collected from the mice 8 days after immunization and analyzed for total and OVA-specific immunoglobulin levels by ELISA. Each circle represents the percent of (A) CD44⁺ T cells producing cytokine or (B) the Ig amounts from an individual mouse. Open circles indicate that the chimera was Ndfip1^+/+, whereas closed circles represent Ndfip1^−/− chimeras.

Figure 7

Ndfip1 Interacts with Itch and Promotes Degradation of JunB (A) T cells were isolated from the spleens and lymph nodes of Ndfip1^+/+ and Ndfip1^−/− mice and cultured in media alone or stimulated 24 hr with anti-CD3 and anti-CD28. Cell lysates were immunoblotted with antibodies against Itch, Ndfip1, or β-actin. (B) Ndfip1^+/+ and Ndfip1^−/− T cells were lysed directly after isolation (U) or cultured in the presence of anti-CD3 and anti-CD28 (S). Lysates were immunoprecipitated with an anti-Itch antibody and blots were probed for Itch and Ndfip1. (C) Ndfip1^+/+ and Ndfip1^−/− T cells were stimulated for the times points indicated and then fixed, permeabilized, and stained for intracellular Itch and Ndfip1. (D) Ndfip1^+/+ and Ndfip1^−/− T cells were isolated and depleted for CD44⁺ cells. Cells were then cultured in media alone or stimulated for 2 or 6 hr or stimulated for 6 hr with cyclohexamide added for the last 4 hr of stimulation. Numbers represent JunB amounts normalized to unstimulated controls for each genotype. Degradation of JunB is measured by comparing lane 4 versus lane 2 for each genotype. (E) Ndfip1^−/− and Ndfip1^+/+ T cell lines were transduced with the empty MIG retrovirus (MMLV-IRES-eGFP) or a Flag-tagged Ndfip1 containing MIG retrovirus. GFP⁺ cells were sorted and JunB degradation was analyzed as described in (D). (F) T cells were directly isolated from an 8- to 10-week-old Ndfip1^+/+ and Ndfip1^−/− mice and WCL were analyzed for JunB protein amounts. β-actin is shown as a control for protein loading. LC, light chain.