Discovery of a novel splice variant of Fcar (CD89) unravels sequence segments necessary for efficient secretion: A story of bad signal peptides and good ones that nevertheless do not make it

Variable-heavy (VH) families influencing IgA1&2 engagement to the antigen, FcαRI and superantigen proteins G, A, and L

Interest in IgA as an alternative antibody format has increased over the years with much remaining to be investigated in relation to interactions with immune cells. Considering the recent whole antibody investigations showing significant distal effects between the variable (V) and constant (C)- regions that can be mitigated by the hinge regions of both human IgA subtypes A1 and A2, we performed an in-depth mechanistic investigation using a panel of 28 IgA1s and A2s of both Trastuzumab and Pertuzumab models. FcαRI binding were found to be mitigated by the differing glycosylation patterns in IgA1 and 2 with contributions from the CDRs. On their interactions with antigen-Her2 and superantigens PpL, SpG and SpA, PpL was found to sterically hinder Her2 antigen binding with unexpected findings of IgAs binding SpG at the CH2-3 region alongside SpA interacting with IgAs at the CH1. Although the VH3 framework (FWR) is commonly used in CDR grafting, we found the VH1 framework (FWR) to be a possible alternative when grafting IgA1 and 2 owing to its stronger binding to antigen Her2 and weaker interactions to superantigen Protein L and A. These findings lay the foundation to understanding the interactions between IgAs and microbial superantigens, and also guide the engineering of IgAs for future antibody applications and targeting of superantigen-producing microbes.

To Plate or to Simply Unfreeze, That Is the Question for Optimal Plasmid Extraction

Many molecular biology applications require fast plasmid DNA extraction, spurring multiple studies on how to speed up the process. It is regularly instructed in standard laboratory protocols to plate out frozen glycerol bacterial stocks prior to bacteria incubation in liquid media and subsequent plasmid extraction, although the rationale for this is often unexplained (other than for the isolation of single colonies). Given the commonality and importance of this laboratory operation, such a practice is time-consuming and laborious. To study the impact of this practice and the alternative direct culturing method, we investigated the association between bacterial cell mass and its potential influence on plasmid yields from the 2 methods. Our results showed no difference with preplating for 7 out of 8 plasmid constructs used in the study, suggesting that direct glycerol recovery would not lead to poorer plasmid yields. The findings support the rationale for direct glycerol recovery for plasmid extraction, without the need of an intermediate preplating step.

Perspective: The promises of a holistic view of proteins-impact on antibody engineering and drug discovery

The reductionist approach is prevalent in biomedical science. However, increasing evidence now shows that biological systems cannot be simply considered as the sum of its parts. With experimental, technological, and computational advances, we can now do more than view parts in isolation, thus we propose that an increasing holistic view (where a protein is investigated as much as a whole as possible) is now timely. To further advocate this, we review and discuss several studies and applications involving allostery, where distant protein regions can cross-talk to influence functionality. Therefore, we believe that an increasing big picture approach holds great promise, particularly in the areas of antibody engineering and drug discovery in rational drug design.

Role of FcαR EC2 region in extracellular membrane localization

The FcαR receptor (CD89) binds to the constant region of Immunoglobulin (Ig) A to mediate mucosal immunity [1-2]. FcαR consist of five exons: two that code for the signal peptide regions S1 & S2, two for the extracellular regions EC1 and EC2, and the final exon for the transmembrane/cytoplasmic tail region [3]. Previously, we reported that the EC1 region plays an essential role for extracellular membrane localization of the receptor [4], where the absence of EC1 would prevent the variants from localizing to the cell surface, even with a full signal peptide. In the case of FcαR Variant 4 (lacking the S2 region only), there was some "leakiness" to membrane surface localization.