Mammals continually confront microbes at mucosal surfaces. A current model suggests that

The glycoprotein genes of Ehrlichia chaffeensis (1,644 bp) and Ehrlichia canis (2,064 bp) encode proteins of 548 to 688 amino acids with predicted molecular masses of only 61 and 73 kDa but with electrophoretic mobilities of 120 kDa (P120) and 140 kDa (P140), respectively. The 120-kDa protein gene of E. chaffeensis contains four identical 240-bp tandem repeat units, and the 140-kDa protein gene of E. canis has 14 nearly identical, tandemly arranged 108-bp repeat units. Conserved serine-rich motifs identified in the repeat units of P120 and P140 were also found in the repeat units of the human granulocytotropic ehrlichiosis agent 130-kDa protein and of the fimbria-associated adhesin protein Fap1 of Streptococcus parasanguis. Nearly the entire (99%) E. chaffeensis P120 gene (1,616 bp), the 14-repeat region (78%) of the E. canis P140 gene (1,620 bp), and a 2-repeat region from the E. chaffeensis P120 gene (520 bp) were expressed in Escherichia coli. The recombinant proteins exhibited molecular masses ranging from 1.6 to 2 times larger than those predicted by the amino acid sequences. Antibodies against the recombinant proteins reacted with E. chaffeensis P120 and E. canis P140, respectively. Carbohydrate was detected on the E. chaffeensis and E. canis recombinant proteins, including the two-repeat polypeptide region of E. chaffeensis P120. A carbohydrate compositional analysis identified glucose, galactose, and xylose on the recombinant proteins. The presence of only one site for N-linked (Asn-Xaa-Ser/Thr) glycosylation, a lack of effect of N-glycosidase F, the presence of 70 and 126 Ser/Thr glycosylation sites in the repeat regions of P120 and P140, respectively, and a high molar ratio of carbohydrate to protein suggest that the glycans may be O linked.Ehrlichia chaffeensis and Ehrlichia canis are obligate intracellular bacteria that exhibit tropism for monocytes and macrophages and are responsible for the diseases human monocytotropic ehrlichiosis and canine ehrlichiosis, respectively (10). Recently, the 120-and 140-kDa protein genes from E. chaffeensis and E. canis have been cloned, expressed, and characterized (18,19). The 120-kDa protein (P120) of E. chaffeensis and the 140-kDa protein (P140) of E. canis are immunodominant and E. chaffeensis P120 appears to be surface exposed (9a). The proteins are homologous, and each has a region of serine-rich tandem repeats. The recombinant E. canis P140 and E. chaffeensis P120 exhibit molecular masses much larger than those predicted by the amino acid sequences, and antibodies produced against the recombinant proteins recognized native E. chaffeensis and E. canis proteins of similar sizes (18,19). Two proteins (P100 and P130) from the human granulocytotropic erhlichiosis (HGE) agent have also been cloned, and the recombinant proteins exhibited higher-than-predicted molecular masses (12).The existence of glycoproteins in eukaryotic cells has been known for years and was thought to be restricted to these cells. However, more recently, glycoproteins have been identified in e...

Differentiated thyroid carcinomas are the most frequent endocrine neoplasms, but account for few cancer-related deaths. Although the indolent growth of these cancers correlates well with longevity, the biological basis for this good prognosis is not known. In contrast, two of the most frequent autoimmune diseases involve the thyroid suggesting a high propensity for this organ to invoke destructive immunity. Unfortunately, the mechanism linking malignancy and autoimmunity is not clear, although the expression of the oncogenic fusion protein RET/PTC3 (RP3) in both of these disorders may provide a clue. Interestingly, the signaling caused by activated RET kinase involves overlapping pathways and some common to the inflammatory response. Accordingly, we analyzed the function of RP3 and a mutant RP3 molecule to induce proinflammatory pathways in thyroid epithelial cells. Indeed, we find that RP3 alone causes increases in nuclear NF-jB activity and secretion of MCP-1 and GM-CSF. Finally, transfer of RP3-expressing thyrocytes into mice in vivo attracted dense macrophage infiltrates, which lead to rapid thyroid cell death. Further, cytokine synthesis and inflammation was largely abrogated by mutation of RP3 Tyr 588 ; an important protein-binding site for downstream signaling. Together, these studies implicate oncogeneinduced cytokine-signaling pathways in a new mechanism linking inflammation with cancer.