Cell surface expression of the 300 kDa mannose-6-phosphate receptor by activated T lymphocytes

Click-Chemistry-Mediated Cell Membrane Glycopolymer Engineering to Potentiate Dendritic Cell Vaccines

Dendritic cell vaccine (DCV) holds great potential in tumor immunotherapy owing to its potent ability in eliciting tumor-specific immune responses. Aiming at engineering enhanced DCV, we report the first effort to construct a glycopolymer-engineered DC vaccine (G-DCV) via metabolicglycoengineering and copper-free click-chemistry. Model G-DCV was prepared by firstly delivering tumor antigens, ovalbumin (OVA) into dendritic cells (DC) with fluoroalkane-grafted polyethyleneimines, followed by conjugating glycopolymers with a terminal group of dibenzocyclooctyne (DBCO) onto dendritic cells. Compared to unmodified DCV, our G-DCV could induce stronger T cell activation due to the enhanced adhesion between DCs and T cells. Notably, such G-DCV could more effectively inhibit the growth of the mouse B16-OVA (expressing OVA antigen) tumor model after adoptive transfer. Moreover, by combination with an immune checkpoint inhibitor, G-DCV showed further increased anti-tumor effects in treating different tumor models. Thus, our work provides a novel strategy to enhance the therapeutic effectiveness of DC vaccines.

Lysosomal Acid Lipase: From Cellular Lipid Handler to Immunometabolic Target

Lysosomal acid lipase (LAL) hydrolyzes cholesteryl esters (CEs) and triglycerides (TGs) to free cholesterol (FC) and free fatty acids (FFAs), which are then used for metabolic purposes in the cell. The process also occurs in immune cells that adapt their metabolic machinery to cope with the different energetic requirements associated with cell activation, proliferation, and polarization. LAL deficiency (LALD) causes severe lipid accumulation and affects the immunometabolic signature in animal models. In humans, LAL deficiency is associated with a peculiar clinical immune phenotype, secondary hemophagocytic lymphohistiocytosis. These observations suggest that LAL might play an important role in cellular immunometabolic modulation, and availability of an effective enzyme replacement strategy makes LAL an attractive target to rewire the metabolic machinery of immune cells beyond its role in controlling cellular lipid metabolism.

Unravelling novel functions of the endosomal transporter mannose 6-phosphate/insulin-like growth factor receptor (CD222) in health and disease: An emerging regulator of the immune system

Properly balanced cellular responses require both the mutual interactions of soluble factors with cell surface receptors and the crosstalk of intracellular molecules. In particular, immune cells exposed unceasingly to an array of positive and negative stimuli must distinguish between what has to be tolerated and attacked. Protein trafficking is one of crucial pathways involved in this labour. The approximately >270-kDa protein transporter called mannose 6- phosphate/insulin-like growth factor 2 receptor (M6P/IGF2R, CD222) is a type I transmembrane glycoprotein present largely intracellularly in the Golgi apparatus and endosomal compartments, but also at the cell surface. It is expressed ubiquitously in a vast majority of higher eukaryotic cell types. Through binding and trafficking multiple unrelated extracellular and intracellular ligands, CD222 is involved in the regulation of a plethora of functions, and thus implicated in many physiological but also pathophysiological conditions. This review describes, first, general features of CD222, such as its evolution, genomic structure and regulation, protein structure and ligands; and second, its specific functions with a special focus on the immune system.

mTORC1 regulates mannose-6-phosphate receptor transport and T-cell vulnerability to regulatory T cells by controlling kinesin KIF13A

Mannose-6-phosphate receptor (M6PR) that facilitates cellular uptake of M6P-bearing proteins, including serine-protease granzyme-B (Gzm-B) has an important role in T-cell activation, migration and contraction. However, molecular mechanisms controlling M6PR expression in T cells remain poorly understood. Here, we show that M6PR expression on T cells is distinctively controlled by two common γ-chain cytokines interleukin-2 (IL-2) and IL-7, and the differential M6PR expression is not caused by an altered synthesis of M6PR protein, but is a result of distinct regulation of kinesin-3 motor-protein KIF13A that transport M6PR onto cell surfaces. Using signaling pathway-specific inhibitors, we determine that IL-2 and IL-7 distinctly regulate KIF13A and β1-adaptin and cell-surface M6PR by controlling a kinase mammalian target of rapamycin complex-1 (mTORC1). Inflammatory cytokine IL-2 and prosurvival cytokine IL-7 induce strong and weak activation of mTORC1, leading to up- and downregulation of motor-protein KIF13A and KIF13A-motorized M6PR on T cells, and formation of IL-2 and IL-7 effectors with M6PR^high and M6PR^low cell-surface expression, respectively. Inhibition of mTORC1 by rapamycin reduces T-cell expression of KIF13A and cell-surface M6PR, and increases T-cell survival in Listeria monocytogenes-infected mice. Using regulatory T (T_reg)-cell-enriched mouse tumor model, we determine that M6PR^high IL-2 effectors but not M6PR^low IL-7 effectors adoptively transferred into tumors are vulnerable to T_reg Gzm-B-mediated cell apoptosis. Inhibition of mTORC1 or small interfering RNA-mediated knockdown of KIF13A or M6PR renders IL-2 effectors refractory to T_reg Gzm-B lethal hit. Overall, our data offer novel mechanistic insights into T-cell M6PR regulation, and T_reg-resistant/T_reg-susceptible phenomenon. Furthermore, regulation of T-cell fate vis-à-vis T_reg suppression via the mTORC1-KIF13A-M6PR axis provides a proof of concept for therapeutic strategies to target cancer, infectious and autoimmune diseases.

The late endosomal transporter CD222 directs the spatial distribution and activity of Lck

The spatial and temporal organization of T cell signaling molecules is increasingly accepted as a crucial step in controlling T cell activation. CD222, also known as the cation-independent mannose 6-phosphate/insulin-like growth factor 2 receptor, is the central component of endosomal transport pathways. In this study, we show that CD222 is a key regulator of the early T cell signaling cascade. Knockdown of CD222 hampers the effective progression of TCR-induced signaling and subsequent effector functions, which can be rescued via reconstitution of CD222 expression. We decipher that Lck is retained in the cytosol of CD222-deficient cells, which obstructs the recruitment of Lck to CD45 at the cell surface, resulting in an abundant inhibitory phosphorylation signature on Lck at the steady state. Hence, CD222 specifically controls the balance between active and inactive Lck in resting T cells, which guarantees operative T cell effector functions.

The Development of Novel Therapies for Rheumatoid Arthritis

BACKGROUND: Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory disease that affects approximately 0.5 to 1 percent of the adults worldwide and commonly results in joint destruction and significant impairment in the quality of life. RA is considered as an autoimmune disease with unknown etiology. Many pathogenic pathways of RA have been revealed recently, which led to development of various novel therapies. OBJECTIVE: The current treatments of RA include 4 categories: non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, non-biologic disease-modifying anti-rheumatic drugs (DMARDs) and biologic DMARDs. In this review, we will discuss some of the most recent development in antirheumatic therapies. METHODS: Using SciFinder Scholar and PubMed as main searching tools, we evaluated various newly developed therapies for RA. Under each drug category, emphases are placed on the mode of action, limitation of the drugs and new drug candidates from the patents search. Those well-established therapies will only be reviewed briefly. CONCLUSION: During the past 20 years, most of the development of new therapies is in DMARDs, especially biological DMARDs. With the discovery of new pathways and the application of drug delivery strategies, more growth is anticipated in this research field.

Chickenpox

PURPOSE OF REVIEW

Varicella-zoster virus (VZV) remains a public health issue around the globe despite the availability of a live attenuated vaccine and several highly active antiviral agents. A program of universal infant vaccination against varicella was introduced in the US almost 10 years ago. Epidemiological data continue to accumulate that will inform decision-making on vaccine use elsewhere. These findings, together with relevant advances in VZV virology, form the substance of this review.

RECENT FINDINGS

Understanding of the pathogenesis of varicella has significantly advanced with the demonstration that the cation-independent mannose 6-phosphate receptor is critical to both entry and egress of enveloped VZV. While our knowledge of intervening events remains sketchy, the future study of VZV will be facilitated by the recent successful cloning of the VZV genome into a bacterial artificial chromosome. Models of latency and reactivation are also being developed, which may help us to understand the epidemiology of herpes zoster in vaccinated populations. Continued evidence of decline in the incidence of varicella, associated hospitalizations and deaths suggests that the vaccine as used in the US is highly effective. However, rates of breakthrough disease are significant and sufficient to sustain outbreaks, even among highly vaccinated populations. This is so despite the generally reduced infectiousness of varicella occurring in vaccinated individuals. There is some evidence of attrition of the immune response over time following immunization in a small proportion of vaccinees.

SUMMARY

Our ability to prevent and treat varicella still outstrips our knowledge of pathogenetic and immune mechanisms. Further clinical advances are likely to arise from growing understanding of VZV biology.

The intracellular granzyme B inhibitor, proteinase inhibitor 9, is up-regulated during accessory cell maturation and effector cell degranulation, and its overexpression enhances CTL potency

Granzyme B (grB) is a serine proteinase released by cytotoxic lymphocytes (CLs) to kill abnormal cells. GrB-mediated apoptotic pathways are conserved in nucleated cells; hence, CLs require mechanisms to protect against ectopic or misdirected grB. The nucleocytoplasmic serpin, proteinase inhibitor 9 (PI-9), is a potent inhibitor of grB that protects cells from grB-mediated apoptosis in model systems. Here we show that PI-9 is present in CD4(+) cells, CD8(+) T cells, NK cells, and at lower levels in B cells and myeloid cells. PI-9 is up-regulated in response to grB production and degranulation, and associates with grB-containing granules in activated CTLs and NK cells. Intracellular complexes of PI-9 and grB are evident in NK cells, and overexpression of PI-9 enhances CTL potency, suggesting that cytoplasmic grB, which may threaten CL viability, is rapidly inactivated by PI-9. Because dendritic cells (DCs) acquire characteristics similar to those of target cells to activate naive CD8(+) T cells and therefore may also require protection against grB, we investigated the expression of PI-9 in DCs. PI-9 is evident in thymic DCs (CD3(-), CD4(+), CD8(-), CD45(+)), tonsillar DCs, and DC subsets purified from peripheral blood (CD16(+) monocytes and CD123(+) plasmacytoid DCs). Furthermore, PI-9 is expressed in monocyte-derived DCs and is up-regulated upon TNF-alpha-induced maturation of monocyte-derived DCs. In conclusion, the presence and subcellular localization of PI-9 in leukocytes and DCs are consistent with a protective role against ectopic or misdirected grB during an immune response.