Host defence peptides (HDPs) are critical components of innate immunity. Despite their diversity, they share common features including a structural signature, designated "γ-core motif". We reasoned that for each HDPs evolved from an ancestral γ-core, the latter should be the evolutionary starting point of the molecule, i.e. it should represent a structural scaffold for the modular construction of the full-length molecule, and possess biological properties. We explored the γ-core of human β-defensin 3 (HBD3) and found that it: (a) is the folding nucleus of HBD3; (b) folds rapidly and is stable in human serum; (c) displays antibacterial activity; (d) binds to CD98, which mediates HBD3 internalization in eukaryotic cells; (e) exerts antiviral activity against human immunodeficiency virus and herpes simplex virus; and (f) is not toxic to human cells. These results demonstrate that the γ-core within HBD3 is the ancestral core of the full-length molecule and is a viable HDP per se, since it is endowed with the most important biological features of HBD3. Notably, the small, stable scaffold of the HBD3 γ-core can be exploited to design disease-specific antimicrobial agents.Host defence peptides (HDPs) are a critical component of innate immunity, and represent a first line of defence against infection by a broad spectrum of pathogens. HDP expression is found in the host tissues most exposed to microorganisms (skin and internal epithelia of e.g. the respiratory and gastrointestinal tracts) and in the cells of the immune system (macrophages, lymphocytes, platelets etc.)1 . Since a number of pathogens that are refractory to conventional antibiotics are sensitive to HDPs, there is considerable interest in the development of these peptides as therapeutics 2 . Moreover, it is becoming increasingly clear that these multifunctional peptides exert other functions besides antimicrobial action, for example, they are involved in the immune surveillance against cancer 3 . Accordingly, almost 1,000 different HDPs have been identified 4 . Despite this diversity, all HDPs share the following features: a small size (< 10 kDa), a positive charge at neutral pH, and an amphipathic structure. This secondary structure drives the interaction of HDP with lipid bilayers and, critically, it enables selectivity between

i Human beta-defensins (hBDs) are crucial peptides for the innate immune response and are thus prime candidates as therapeutic agents directed against infective diseases. Based on the properties of wild-type hBD1 and hBD3 and of previously synthesized analogs (1C, 3I, and 3N), we have designed a new analog, 3NI, and investigated its potential as an antimicrobial drug. Specifically, we evaluated the antimicrobial activities of 3NI versus those of hBD1, hBD3, 1C, 3I, and 3N. Our results show that 3NI exerted greater antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis than did hBD1 and hBD3, even with elevated salt concentrations. Moreover, its antiviral activity against herpes simplex virus 1 was greater than that of hBD1 and similar to that of hBD3. Subsequently, we investigated the cytotoxic effects of all peptides in three human epithelial carcinoma cell lines: A549 from lung, CaCo-2 from colon, and Capan-1 from pancreas. None of the analogs significantly reduced cell viability versus wild-type hBD1 and hBD3. They did not induce genotoxicity or cause an increase in the number of apoptotic cells. Using confocal microscopy, we also investigated the localization of the peptides during their incubation with epithelial cells and found that they were distributed on the cell surface, from which they were internalized. Finally, we show that hBD1 and hBD3 are characterized by high resistance to serum degradation. In conclusion, the new analog 3NI seems to be a promising anti-infective agent, particularly given its high salt resistance-a feature that is relevant in diseases such as cystic fibrosis.

We prove that the SH2-containing tyrosine phosphatase 1 (SHP-1) plays a prominent role as resistance determinant of imatinib (IMA) treatment response in chronic myelogenous leukemia cell lines (sensitive/ KCL22-S and resistant/KCL22-R). Indeed, SHP-1 expression is significantly lower in resistant than in sensitive cell line, in which coimmunoprecipitation analysis shows the interaction between SHP-1 and a second tyrosine phosphatase SHP-2, a positive regulator of RAS/MAPK pathway.In KCL22-R SHP-1 ectopic expression restores both SHP-1/SHP-2 interaction and IMA responsiveness; it also decreases SHP-2 activity after IMA treatment. Consistently, SHP-2 knocking-down in KCL22-R reduces either STAT3 activation or cell viability after IMA exposure. Therefore, our data suggest that SHP-1 plays an important role in BCR-ABL-independent IMA resistance modulating the activation signals that SHP-2 receives from both BCR/ABL and membrane receptor tyrosine kinases. The role of SHP-1 as a determinant of IMA sensitivity has been further confirmed in 60 consecutive untreated patients with chronic myelogenous leukemia, whose SHP-1 mRNA levels were significantly lower in case of IMA treatment failure (P < .0001). In conclusion, we suggest that SHP-1 could be a new biologic indicator at baseline of IMA sensitivity in patients with chronic myelogenous leukemia. (Blood. 2011;118(13): 3634-3644) IntroductionImatinib (IMA)-targeted inhibition of BCR-ABL is considered the standard front-line therapy for chronic myelogenous leukemia (CML). 1 Although most patients respond to the therapy, primary or acquired resistance to IMA may occur during treatment. 2,3 In addition, the depth of response to the therapy is highly variable: most patients achieve complete cytogenetic remission (CCyR), whereas a more restricted number of them obtains major molecular remission (MMR) and even fewer complete molecular remission. Until now, knowledge of resistance mechanisms is still limited: acquisition of mutations within the kinase domain of BCR-ABL is the main known and common mechanism of resistance. 4 However, ABL mutations seem to be particularly frequent only in acquired resistance or in advanced phases of CML, instead it is less common in front-line resistance. Various BCR-ABL-independent mechanisms of IMA resistance have been proposed, and it is possible that a complex phenomenon of resistance might be sustained by still unknown BCR-ABL-independent molecular mechanisms. [5][6][7] SHP-1 and SHP-2 are two SH2-containing tyrosine phosphatases involved in cell growth regulation. Although they share significant overall sequence identity, they often seem to have opposite biologic functions. 8,9 Indeed, SHP-1 has been described as a negative signal transducer, whereas SHP-2 is a positive regulator of signaling pathways. Note, both SHP-1 and SHP-2 play a role in hematopoietic neoplasias.The activated form of SHP-2, involving phosphorylation at Tyr542 and Tyr580, 10 is associated with GAB1, which is a critical factor to sustain ERK activation downstream of se...

Human β-defensins play a pivotal role in the innate immune response. Although expressed by and acting at epithelial surfaces, little is known about their specific interaction with epithelial structures. Here, we identify the transmembrane protein CD98 as a cell surface receptor involved in the internalization of human β-defensin 3 (hBD3) in human epithelial A549 cells. CD98 and hBD3 extensively colocalize on the basolateral domain of A549. While verifying their direct binding by fluorescence resonance energy transfer and surface plasmon resonance, we mapped the interaction to CD98 residues 304-414, i.e. to the region known to interact with the proteins of intestinal bacteria during colonic invasion. Treatment of A549 cells with hBD3 dramatically reduces CD98 expression and conversely, knockdown of CD98 expression impairs hBD3 cell surface binding and internalization. Competition for bacterial binding to CD98 and downregulation of CD98 expression may represent novel mechanisms for the antibacterial activity of hBD3.