Tonsillar crypt epithelium of palmoplantar pustulosis secretes interleukin-6 to support B-cell development via p63/p73 transcription factors

Palmoplantar pustulosis (PPP) is an autoimmune disease characterized by psoriasis-like erythematous lesions on palms and/or soles due to an abnormal humoral immune response. Tonsillectomy is effectively employed for the treatment of PPP; however, how tonsils are involved in the aetiology of PPP remains unclear. Here we analysed surgically resected palatine tonsils from 36 cases of PPP as well as usual recurrent tonsillitis (RT) as a control. Histological examination revealed that a unique lesion, with lymphoid follicles surrounded by reticular crypt epithelial cells, was more frequently observed in tonsils of patients with PPP than in those with RT (p < 0.0001; PPP vs RT). Interestingly, crypt epithelial cells in primary cultures derived from PPP tonsils showed marked production of interleukin-6 (IL-6). Moreover, these epithelial cells from PPP tonsils expressed p53-related transcription factors in their nuclei that were found to contribute to the up-regulation of IL-6 gene expression. These findings suggest that, at least in part, the specialized lymphoepithelial symbiosis of PPP tonsils, under the control of p53-related factors, may be relevant to the generation of the impaired micro-environment underlying the aberrant production of autoantibodies.

Characterization of acyl-CoA-binding protein (ACBP) in the pheromone gland of the silkworm, Bombyx mori

Various fatty acyl-CoAs are involved as intermediates or precursors of sex pheromone components in the biosynthetic pathway of the pheromones in many lepidopteran insects. We have purified a 10-kDa protein from the cytosolic fraction of Bombyx mori pheromone glands by using affinity chromatography with a palmitoyl-CoA-agarose column and reversed-phase HPLC. Amino acid sequence analysis of the fragment peptides obtained from the purified protein, and a homology search, revealed that this protein was a member of acyl-CoA-binding proteins (ACBPs). MALDI-TOF mass spectral analysis of the purified protein and cloning of the gene from a pheromone gland cDNA library confirmed B. mori ACBP to be a 90 amino acid protein with 78.9% identity to that of Manduca sexta ACBP. The secondary structure of the recombinant B. mori ACBP was determined by NMR spectroscopy. Northern blot analysis demonstrated that B. mori ACBP was predominantly expressed in the pheromone gland and the corresponding transcript was expressed from the day before adult eclosion. Present results suggest that ACBP plays a significant role in the production of sex pheromones regulated by the neurohormone, pheromone biosynthesis activating neuropeptide (PBAN).

Role of the ENTH domain in phosphatidylinositol-4,5-bisphosphate binding and endocytosis

Endocytic proteins such as epsin, AP180, and Hip1R (Sla2p) share a conserved modular region termed the epsin NH2-terminal homology (ENTH) domain, which plays a crucial role in clathrin-mediated endocytosis through an unknown target. Here, we demonstrate a strong affinity of the ENTH domain for phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2]. With nuclear magnetic resonance analysis of the epsin ENTH domain, we determined that a cleft formed with positively charged residues contributed to phosphoinositide binding. Overexpression of a mutant, epsin Lys76 --> Ala76, with an ENTH domain defective in phosphoinositide binding, blocked epidermal growth factor internalization in COS-7 cells. Thus, interaction between the ENTH domain and PtdIns(4,5)P2 is essential for endocytosis mediated by clathrin-coated pits.

Mouse myosin X: molecular architecture and tissue expression as revealed by northern blot and in situ hybridization analyses

The structure of the coding region of mouse myosin X cDNA was determined. The predicted protein sequence indicated an approximately 240 kDa molecular mass with 2062 amino acids. When aligned with the structure predicted for calf myosin X (GenBank Accession No. U55042), extremely highly conserved pleckstrin homology domains and a myosin tail homology 4 domain were apparent in the tail region, suggesting their importance for myosin X's function. Northern blot analysis revealed the existence of a myosin X mRNA, 8.7 kb in size, in various mouse tissues, while a similar size of human type myosin X mRNA was recognized mainly in the testis. In addition to the adult-type transcripts in mice, a smaller embryo-specific mRNA, 4.8 kb in size, was identified in early to late embryonic stages, suggesting the presence of a shorter myosin X isoform in mouse embryos. In situ hybridization experiments with mouse testis revealed that myosin X mRNA was restricted to Sertoli cells at stages VIII-X of the spermatogenesis cycle, suggesting that myosin X is implicated in the supporting cells during the spermatid morphogenesis.

Solution structure of the Eps15 homology domain of a human POB1 (partner of RalBP1)

The solution structure of the Eps15 homology (EH) domain of a human POB1 (partner of RaIBP1) has been determined by uniform 13C/15N labeling and heteronuclear multidimensional nuclear magnetic resonance spectroscopy. The POB1 EH domain consists of two EF-hand structures, and the second one binds a calcium ion. In the calcium-bound state, the orientation of the fourth alpha-helix relative to the other helices of the POB1 EH domain is slightly different from that of calbindin, and much more different from those of calmodulin and troponin C, on the basis of their atomic coordinates.

The solution structure of the pleckstrin homology domain of mouse Son-of-sevenless 1 (mSos1)

The solution structure of the pleckstrin homology (PH) domain of mouse Son-of-sevenless 1 (mSos1), a guanine nucleotide exchange factor for Ras, was determined by multidimensional NMR spectroscopy. The structure of the mSos1 PH domain involves the fundamental PH fold, consisting of seven beta-strands and one alpha-helix at the C terminus, as determined for the PH domains of other proteins. By contrast, the mSos1 PH domain showed two major characteristic features. First, the N-terminal region, whose amino acid sequence is highly conserved among Sos proteins, was found to form an alpha-helix, which interacts with the beta-sheet structure of the fundamental PH fold. Second, there is a long unstructured loop between beta3 and beta4. Furthermore, the mSos1 PH domain was found to bind phosphatidylinositol-4,5-bisphosphate by a centrifugation assay. The addition of inositol-1,4,5-trisphosphate to the mSos1 PH domain induced backbone amide chemical shift changes mainly in the beta1/beta2 loop and the N- and C-terminal parts of the long beta3/beta4 loop. This inositol-1,4,5-trisphosphate-binding mode of the mSos1 PH domain is somewhat similar to those of the PH domains of pleckstrin and phospholipase Cdelta1, and is clearly different from those of other PH domains.