Gabriele Bon

This was followed by the addition of neuraminidase solution or buffer control to each well and continued resistance measurement 4 (or more) h. AAV6 relies more on sialic acid or sialic acid-containing glycoproteins than AAV1 for cell entry and/or subsequent steps of infection. Neuraminidases are enzymes that cleave via hydrolysis α(2-3)-, α(2-6)-, and α(2-8)-linked terminal sialic acid residues bound to Gal, GlcNac, GalNAc, AcNeu, or GlyNeu residues of oligosaccharides, glycolipids, and glycoproteins (17). Neuraminidases from different sources exhibit different specificities for sialic acid linkages hydrolyzed (4, 24). The lectin from Arachis hypogaea binds to the sequence Gal(β1,3)GalNAc, also known as T-antigen (19, 24). When the T-antigen sequence is sialylated, lectin from Arachis hypogaea does not bind to the disaccharide (10). However, as in the case of red blood cells, following treatment with neuraminidase, the T-antigen is exposed on the cell surface allowing the lectin to bind (19). Indeed, this approach has already been used to demonstrate loss of sialic acids from pulmonary endothelial cell surfaces (26). For these experiments, PAECs and PMVECs were treated with neuraminidase from Clostridium perfringens, which cleaves α(2-3)-, α(2-6)-, and α(2-8)-terminal sialic acid residues (3, 4, 17). For more info on Supplier of sialic acid powder as Raw Material for pharmaceuticals review our webpage. The Arachis hypogaea lectin did not bind to control cells but exhibited strong binding to neuraminidase-treated cells as evidenced by positive fluorescence in treated cells (Fig. 2B), revealing the underlying Gal(β1,3)GalNAc epitope.

The formula protein sources (whey vs casein) did not have a large impact on the ratios of free to bound sialic acids, nor did protein hydrolysis or sample form (solid vs liquid). Whole cell lysate (20 μl) was combined with 80 μl of 0.05 N H2SO4 (hydrolysis reagent) and incubated at 80°C for 60 min. Samples were briefly centrifuged at 14,000 revolution/min (16,000 g), after which 20 μl of 1 M NaOH (neutralization reagent) was added and the mixture centrifuged again at 14,000 revolution/min. For free sialic acid measurement, whole cell lysate samples were used; for total sialic acid measurement, hydrolyzed cell lysate samples were used. Cultures were stained with FITC-labeled lectins that bind to three different carbohydrates as follows: WGA binds sialic acid in any linkage, MAA binds 2,3-linked sialic acid, and SNA binds 2,6-linked sialic acid. A: confluent monolayers of PAECs and PMVECs were treated with FITC-tagged Maackia amurensis agglutinin (MAA). A: total and free sialic acids expressed by PAECs and PMVECs were quantitated. One way in which sialic expression can differ is in quantity; however, the sialic acid levels did not differ significantly between PAECs and PMVECs.

Pulmonary artery endothelial cells (PAECs) and pulmonary microvascular endothelial cells (PMVECs) express sialic acids. In summation, our results have established that terminally linked sialic acids are critical determinants of pulmonary endothelial barrier function. Additionally, it will be important to determine whether acetylated sialic acids or (2,8) dimeric-linked sialic acids play a key role in determining barrier integrity. B: PAECs and PMVECs were treated with neuraminidase from Clostridium perfringens to cleave terminal sialic acids. On the other hand, only PAECs exhibited strong SNA binding, reflective of α(2,6)-linked sialic acids (Fig. 3B). Although SNA staining was also observed in regions of cell-cell contact, it appeared to be somewhat more diffuse compared with the distinct MAA staining. Sialic acid quantitation was carried out using the Sialic Acid (NANA) Assay kit from Biovision (Mountain View, CA) following the manufacturer's protocol. For their proper use, follow the manufacturer's instructions (see, for example, EasyPrepJ, FlexiPrepJ, both from Pharmacia Biotech; StrataCleanJ, from Stratagene; and, QIAexpress Expression System, Qiagen). Protease activity in neuraminidase preparations was measured using the Pierce Fluorescent Protease Assay Kit (Thermo Scientific, Rockford, IL) following manufacturer's instructions. Electric cell-substrate impedance sensing (ECIS) experiments were conducted using an Applied Biophysics Model 1600R instrument (Applied Biophysics, Troy, NY).

An alternative is the enzymatic synthesis of Neu5Ac from N-acetylmannosamine (ManNAc) and pyruvate using the N-acetylneuraminic acid aldolase. Transcription termination signals, enhancers, and other nucleic acid sequences that influence gene expression, can also be included in an expression cassette. For example, a single extrachromosomal vector can include multiple expression cassettes or more that one compatible extrachromosomal vector can be used maintain an expression cassette in a host cell. Plasmids containing one or more of the above listed components employs standard ligation techniques as described in the references cited above. The report includes in-detail references of all the notable product categories as well as application specifications. These questions as well as the detailed examinations of the complete glycan structures, identities, and sequences of underlying tethering proteins are the focus of our ongoing studies. In addition, we determined by inhibitor (N-benzyl GalNAc)- and cell line-specific (Lec-1) studies that AAV1 and AAV6 require N-linked and not O-linked sialic acid. At the concentration of 1 mM, N-benzyl GalNac inhibited AAV4 transduction by 10-fold. In contrast, only marginal or no inhibition was seen for AAV1, AAV6, or AAV2 transduction, indicating that AAV1 and AAV6 do not use O-linked sialic acid for transduction. Pulmonary endothelial cell barrier integrity is dependent on sialic acid presence.