Guardians at the gate

Patent protection and FDA exclusivities are the two principal forms of protection available to companies that develop therapeutic monoclonal antibodies. Proposed changes to both forms of protection are currently being debated in the United States Congress. Specifically, Congress is presently debating both biosimilar and patent reform legislations. Although no bill has yet passed, it is expected that patent reform legislation should pass this year. It is less likely that a biosimilar bill will pass this year. However, when legislations are enacted, the changes will significantly impact the business of therapeutic monoclonal antibodies.     

Guardians at the gate

Patents provide one of the few protections companies can avail themselves of to help protect their therapeutic monoclonal antibody products. Just as the therapeutic monoclonal antibody field is constantly evolving, so too is the legal environment surrounding these inventions. In a series of articles, the general state of the law surrounding therapeutic antibodies will be explained, and important challenges to this technology area will be discussed. Much is at stake when companies market therapeutic monoclonal antibodies; therefore, a firm understanding of this important form of protection is critically important for anyone developing such products.     

Guardians of the actin monomer

Actin is a universal force provider in eukaryotic cells. Biological processes harness the pressure generated from actin polymerization through dictating the time, place and direction of filament growth. As such, polymerization is initiated and maintained via tightly controlled filament nucleation and elongation machineries. Biological systems integrate force into their activities through recruiting and activating these machineries. In order that actin function as a common force generating polymerization motor, cells must maintain a pool of active, polymerization-ready monomeric actin, and minimize extemporaneous polymerization. Maintenance of the active monomeric actin pool requires the recycling of actin filaments, through depolymerization, nucleotide exchange and reloading of the polymerization machineries, while the levels of monomers are constantly monitored and supplemented, when needed, via the access of a reserve pool of monomers and through gene expression. Throughout its monomeric life, actin needs to be protected against gratuitous nucleation events. Here, we review the proteins that act as custodians of monomeric actin. We estimate their levels on a tissue scale, and calculate the implied concentrations of each actin complex based on reported binding affinities. These estimations predict that monomeric actin is rarely, if ever, alone. Thus, the guardians keep the volatility of actin in check, so that its explosive power is only released in the controlled environments of the nucleation and polymerization machineries.     

Mitochondrial Hexokinases: Guardians of the Mitochondria

There is accumulating evidence that cell survival and metabolism are inexorably linked. As a majormediator of both the metabolic and anti-apoptotic effects of growth factors, the serine/threonine kinaseAkt (also known as protein kinase B or PKB) is particularly well-suited to coordinate the regulation ofthese interrelated processes. Recent demonstrations that growth factors and Akt require glucose (Glc) toprevent apoptosis and promote cell survival are compatible with this contention, as is a positivecorrelation between Akt-regulated mitochondrial hexokinase (mtHK) association and apoptoticresistance. From a phylogenetic perspective, the ability of Akt to regulate cellular metabolismapparently preceded the capacity to control cell survival, suggesting an evolutionary basis for the Glcdependent anti-apoptotic effects of Akt. We speculate that, somewhere in the course of evolution, themetabolic regulatory function of Akt evolved into an adaptive sensing system involving mtHK thatensures mitochondrial homeostasis, thereby coupling metabolism to cell survival. We also propose thatthis “guardian” function of mtHK may be specifically exploited for therapeutic purposes.     

Guardian at the gate: preventing unspliced pre-mRNA export

The production of a mature mRNA requires the assembly and cooperation of numerous complexes before nuclear export. The deleterious effects of intron-containing pre-mRNA leakage into the cytoplasm necessitate mechanisms to prevent premature export of partially processed or unprocessed messages. A new study demonstrates that the Saccharomyces cerevisiae protein Mlp1 specifically retains intron-containing pre-mRNAs in the nucleus.     

Signaling at the gate: Phosphorylation of the mitochondrial protein import machinery

Protein import into mitochondria is an essential process in every eukaryotic organism. While most of the components of the import machinery have been identified and are mechanistically quite well understood, regulation of this process had been a largely neglected area of research in the past. Recently, we demonstrated for the first time that the translocase of the outer mitochondrial membrane (TOM) is phosphorylated and regulated by several cytosolic protein kinases. Among these, casein kinase 2 (CK2) governs the assembly of TOM complexes, while protein kinase A (PKA) controls translocase function. Here, we outline the current model of protein import regulation, together with additional mitochondrial functions of CK2 and PKA. We also reflect the data on mitochondria-associated protein kinases and phosphatases in the model organism baker's yeast.     

RhoGTPases and inflammasomes: Guardians of effector-triggered immunity

Pathogens have evolved smart strategies to invade hosts and hijack their immune responses. One such strategy is the targeting of the host RhoGTPases by toxins or virulence factors to hijack the cytoskeleton dynamic and immune processes. In response to this microbial attack, the host has evolved an elegant strategy to monitor the function of virulence factors and toxins by sensing the abnormal activity of RhoGTPases. This innate immune strategy of sensing bacterial effector targeting RhoGTPase appears to be a bona fide example of effector-triggered immunity (ETI). Here, we review recently discovered mechanisms by which the host can sense the activity of these toxins through NOD and NOD-like receptors (NLRs).     

Warriors at the gate that never sleep: non-host resistance in plants

The native resistance of most plant species against a wide variety of pathogens is known as non-host resistance (NHR), which confers durable protection to plant species. Only a few pathogens or parasites can successfully cause diseases. NHR is polygenic and appears to be linked with basal plant resistance, a form of elicited protection. Sensing of pathogens by plants is brought about through the recognition of invariant pathogen-associated molecular patterns (PAMPs) that trigger downstream defense signaling pathways. Race-specific resistance, (R)-gene mediated resistance, has been extensively studied and reviewed, while our knowledge of NHR has advanced only recently due to the improved access to excellent model systems. The continuum of the cell wall (CW) and the CW-plasma membrane (PM)-cytoskeleton plays a crucial role in perceiving external cues and activating defense signaling cascades during NHR. Based on the type of hypersensitive reaction (HR) triggered, NHR was classified into two types, namely type-I and type-II. Genetic analysis of Arabidopsis mutants has revealed important roles for a number of specific molecules in NHR, including the role of SNARE-complex mediated exocytosis, lipid rafts and vesicle trafficking. As might be expected, R-gene mediated resistance is found to overlap with NHR, but the extent to which the genes/pathways are common between these two forms of disease resistance is unknown. The present review focuses on the various components involved in the known mechanisms of NHR in plants with special reference to the role of CW-PM components.