The tight junction protein ZO-1 belongs to a family of multidomain proteins known as the membrane-associated guanylate kinase homologs (MAGUKs). ZO-1 has been demonstrated to interact with the transmembrane protein occludin, a second tight junction-specific MAGUK, ZO-2, and F-actin, although the nature and functional significance of these interactions is poorly understood. To further elucidate the role of ZO-1 within the epithelial tight junction, we have introduced epitope-tagged fragments of ZO-1 into cultured MDCK cells and identified domains critical for the interaction with ZO-2, occludin, and F-actin. A combination of in vitro and in vivo binding assays indicate that both ZO-2 and occludin interact with specific domains within the N-terminal (MAGUK-like) half of ZO-1, whereas the unique proline-rich C-terminal half of ZO-1 cosediments with F-actin. Consistent with these observations, we found that a construct encoding the N-terminal half of ZO-1 is specifically associated with tight junctions, whereas the unique C-terminal half of ZO-1 is distributed over the entire lateral surface of the plasma membrane and other actin-rich structures. In addition, we have identified a 244-amino acid domain within the Nterminal half of ZO-1, which is required for the stable incorporation of ZO-1 into the junctional complex of polarized MDCK cells. These observations suggest that one functional role of ZO-1 is to organize components of the tight junction and link them to the cortical actin cytoskeleton.

Currently, no approved monoclonal antibody (mAb) therapies exist for human multiple myeloma (MM). Here we characterized cell surface CS1 as a novel MM antigen and further investigated the potential therapeutic utility of HuLuc63, a humanized anti-CS1 mAb, for treating human MM. CS1 mRNA and protein was highly expressed in CD138-purified primary tumor cells from the majority of MM patients (more than 97%) with low levels of circulating CS1 detectable in MM patient sera, but not in healthy donors. CS1

The complete cDNA sequence for canine ZO-2, a tight junction-specific protein, is presented. A single open reading frame encodes a polypeptide of 1,174 amino acids with a predicted molecular mass of 132,085 daltons. As noted previously (1), ZO-2 is a member of the membraneassociated guanylate kinase-containing (MAGUK) protein family, a family which includes an additional tight junction-associated protein, ZO-1. These proteins contain a region homologous to guanylate kinase, an SH3 domain, and variable numbers of PSD-95/discs-large/ ZO-1 (PDZ) domains, shown to be involved in proteinprotein interactions. ZO-2 and ZO-1 contain three PDZ domains in the N-terminal half of the molecule. Between the first and second PDZ domains, ZO-2 displays a basic region (pI ‫؍‬ 10.27) containing 22% arginine residues. Both ZO-1 and ZO-2 have proline-rich C-terminal regions that are not homologous to other MAGUK family members. Sequence analysis of multiple ZO-2 cDNAs reveals a 36-amino acid domain in this C-terminal region present in only some of the cDNAs. Overall, ZO-2 is highly homologous to ZO-1, showing 51% amino acid identity; however, the C-terminal ends of the molecules show only 25% amino acid identity. This suggests that the C-terminal ends of ZO-1 and ZO-2 have different functions.Several molecular constituents of the tight junction have been identified. These include ZO-1 (2), cingulin (3), ZO-2 (1, 4), 7H6 (5), Rab3B (6), and occludin (7). The presence of other proteins at the tight junction, including spectrin (8, 9), another Rab protein (Rab13) (10), and p130 (11), has been implicated but not confirmed.The complete mouse (12) and human (13) protein and cDNA sequences of ZO-1 have been published. A partial sequence for ZO-2 has also been characterized (1). Analyses of these sequences indicate that ZO-1 and ZO-2 share significant homology with each other and with several other proteins, including the lethal(1)discs-large-1 (dlg) tumor suppressor gene product (dlg-A) of Drosophila (14), erythrocyte membrane-associated p55 (15), and PSD-95/SAP90, a protein found at brain presynaptic membranes (16,17). These proteins share several conserved regions, including a region homologous to guanylate kinase (GUK), 1 an enzyme which converts GMP to GDP, a single src homology (SH3) domain, hypothesized to be involved in protein-protein interactions necessary for signal transduction (18,19), and a variable number of N-terminal repeats termed PDZ domains (from PSD-95, discs-large, ZO-1), shown to bind integral plasma membrane proteins (20 -23). As all proteins in this group are associated with the plasma membrane, they have collectively been termed the MAGUK family (membrane-associated guanylate kinase-containing) (24).ZO-1 and ZO-2 are different from other family members but similar to each other in that they display C-terminal acidic and proline-rich regions (1, 13). ZO-1 also contains an alternatively spliced region, termed the ␣ motif, in the C-terminal region (25,26). The exact function of this splice domain remains unknown. Her...

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Elosulfase alfa is an enzyme replacement therapy for Morquio A syndrome (mucopolysaccharidosis IVA), a multisystemic progressive lysosomal storage disorder. This report includes the primary treatment outcomes and immunogenicity profile of elosulfase alfa in patients with Morquio A syndrome from 2 sequential studies, MOR-002 (ClinicalTrials.govNCT00884949) and MOR-100 (NCT01242111), representing >5 years of clinical study data. MOR-002 was an open-label, single-arm phase 1/2 study that evaluated the pharmacokinetics, safety, immunogenicity, and preliminary efficacy of 3 sequential doses of elosulfase alfa (0.1, 1.0, and 2.0 mg/kg/week) in patients with Morquio A syndrome (n = 20) over 36 weeks, followed by an optional 36- to 48-week treatment period using elosulfase alfa 1.0 mg/kg once weekly (qw). During the 0.1 mg/kg dosing phase, 1 patient discontinued due to a type I hypersensitivity adverse event (AE), and that patient's sibling voluntarily discontinued in the absence of AEs. An additional patient discontinued due to recurrent infusion reactions during the 1.0 mg/kg continuation phase. The remaining 17 patients completed MOR-002 and enrolled in MOR-100, an open-label, long-term extension study that further evaluated safety and clinical outcomes with elosulfase alfa administered at 2.0 mg/kg qw. During the course of MOR-100, patients were given the option of receiving elosulfase alfa infusions at home with nursing assistance. Over the course of both studies, all patients experienced ≥1 AE and most patients experienced a drug-related AE, generally of mild or moderate severity. Hypersensitivity reactions reported as related to study drug occurred in 25% of patients. Thirteen patients who chose to receive infusions at home had the same tolerability and safety profile, as well as comparable compliance rates, as patients who chose to receive on-site infusions. All patients developed antibodies to elosulfase alfa. Positivity for neutralizing antibodies was associated with increased drug half-life and decreased drug clearance. Despite formation of antidrug-binding (total antidrug antibodies, TAb) and in vitro neutralizing antibodies (NAb) in all patients, these types of immunogenicity to elosulfase alfa were not correlated with safety or clinical outcomes. In contrast with the reported natural history of Morquio A, no trends toward decreasing endurance, respiratory function, or ability to perform activities of daily living were observed in this cohort over the 5-year period.