Zn²⁺ deficiency in the human population is frequent in underdeveloped countries. Worldwide, approximatively 2 billion people consume Zn²⁺-deficient diets, accounting for 1–4% of deaths each year, mainly in infants with a compromised immune system. Depending on the severity of Zn²⁺ deficiency, clinical symptoms are associated with impaired wound healing, alopecia, diarrhea, poor growth, dysfunction of the immune and nervous system with congenital abnormalities and bleeding disorders. Poor nutritional Zn²⁺ status in patients with metastatic squamous cell carcinoma or with advanced non-Hodgkin lymphoma, was accompanied by cutaneous bleeding and platelet dysfunction. Forcing Zn²⁺ uptake in the gut using different nutritional supplementation of Zn²⁺ could ameliorate many of these pathological symptoms in humans. Feeding adult rodents with a low Zn²⁺ diet caused poor platelet aggregation and increased bleeding tendency, thereby attracting great scientific interest in investigating the role of Zn²⁺ in hemostasis. Storage protein metallothionein maintains or releases Zn²⁺ in the cytoplasm, and the dynamic change of this cytoplasmic Zn²⁺ pool is regulated by the redox status of the cell. An increase of labile Zn²⁺ pool can be toxic for the cells, and therefore cytoplasmic Zn²⁺ levels are tightly regulated by several Zn²⁺ transporters located on the cell surface and also on the intracellular membrane of Zn²⁺ storage organelles, such as secretory vesicles, endoplasmic reticulum or Golgi apparatus. Although Zn²⁺ is a critical cofactor for more than 2000 transcription factors and 300 enzymes, regulating cell differentiation, proliferation, and basic metabolic functions of the cells, the molecular mechanisms of Zn²⁺ transport and the physiological role of Zn²⁺ store in megakaryocyte and platelet function remain elusive. In this review, we summarize the contribution of extracellular or intracellular Zn²⁺ to megakaryocyte and platelet function and discuss the consequences of dysregulated Zn²⁺ homeostasis in platelet-related diseases by focusing on thrombosis, ischemic stroke and storage pool diseases.

Cancer-associated inflammation has been established as a hallmark feature of almost all solid cancers. Tumor-extrinsic and intrinsic signaling pathways regulate the process of cancer-associated inflammation. Tumor-extrinsic inflammation is triggered by many factors, including infection, obesity, autoimmune disorders, and exposure to toxic and radioactive substances. Intrinsic inflammation can be induced by genomic mutation, genome instability and epigenetic remodeling in cancer cells that promote immunosuppressive traits, inducing the recruitment and activation of inflammatory immune cells. In RCC, many cancer cell-intrinsic alterations are assembled, upregulating inflammatory pathways, which enhance chemokine release and neoantigen expression. Furthermore, immune cells activate the endothelium and induce metabolic shifts, thereby amplifying both the paracrine and autocrine inflammatory loops to promote RCC tumor growth and progression. Together with tumor-extrinsic inflammatory factors, tumor-intrinsic signaling pathways trigger a Janus-faced tumor microenvironment, thereby simultaneously promoting or inhibiting tumor growth. For therapeutic success, it is important to understand the pathomechanisms of cancer-associated inflammation, which promote cancer progression. In this review, we describe the molecular mechanisms of cancer-associated inflammation that influence cancer and immune cell functions, thereby increasing tumor malignancy and anti-cancer resistance. We also discuss the potential of anti-inflammatory treatments, which may provide clinical benefits in RCCs and possible avenues for therapy and future research.

Blood flow–induced hemodynamic changes result in mechanical stress on blood cells and vessel walls. Increased shear stress can activate platelets and other circulating cells, triggering the rapid activation of receptors, calcium channels, and related signaling mechanisms. Shear stress can also modify the folding of extracellular molecules and directly activate mechanosensitive receptors and calcium channels. The mechanical movement of the extracellular matrix and the intracellular cortical actin cytoskeleton can change the conformation of platelet receptors and gate channel pores in the plasma membrane. Mechanosensitive platelet receptors and their downstream signaling events and metabolic products can also indirectly activate calcium channels. While the molecular composite of mechanotransduction pathways has been described in mammals, shear stress–induced platelet receptors and their cross talk with calcium channels have been incompletely characterized. In this review, we discuss current knowledge about the role of mechanosensitive platelet receptors and calcium channels in shear-dependent platelet activation and arterial thrombus formation.

N-glycans are covalently linked to an asparagine residue in a simple acceptor sequence of proteins, called a sequon. This modification is important for protein folding, enhancing thermodynamic stability, and decreasing abnormal protein aggregation within the endoplasmic reticulum (ER), for the lifetime and for the subcellular localization of proteins besides other functions. Hypoglycosylation is the hallmark of a group of rare genetic diseases called congenital disorders of glycosylation (CDG). These diseases are due to defects in glycan synthesis, processing, and attachment to proteins and lipids, thereby modifying signaling functions and metabolic pathways. Defects in N-glycosylation and O-glycosylation constitute the largest CDG groups. Clotting and anticlotting factor defects as well as a tendency to thrombosis or bleeding have been described in CDG patients. However, N-glycosylation of platelet proteins has been poorly investigated in CDG. In this review, we highlight normal and deficient N-glycosylation of platelet-derived molecules and discuss the involvement of platelets in the congenital disorders of N-glycosylation.

Store-operated Ca²⁺ entry (SOCE) is the major route of Ca²⁺ influx in platelets. The Ca²⁺ sensor stromal interaction molecule 1 (STIM1) triggers SOCE by forming punctate structures with the Ca²⁺ channel Orai1 and the inositol trisphosphate receptor (IP₃R), thereby linking the endo-/sarcoplasmic reticulum to the plasma membrane. Here, we identified the BAR domain superfamily member bridging integrator 2 (BIN2) as an interaction partner of STIM1 and IP₃R in platelets. Deletion of platelet BIN2 (Bin2^{fl/fl,Pf4-Cre} mice) resulted in reduced Ca²⁺ store release and Ca²⁺ influx in response to all tested platelet agonists. These defects were a consequence of impaired IP₃R function in combination with defective STIM1-mediated SOC channel activation, while Ca²⁺ store content and agonist-induced IP₃ production were unaltered. This severely defective Ca²⁺ signaling translated into impaired thrombus formation under flow and a protection of Bin2^{fl/fl,Pf4-Cre} mice in models of arterial thrombosis and stroke. Our results establish BIN2 as a central regulator of platelet activation in thrombosis and thrombo-inflammatory disease settings.

BACKGROUND: MAGT1 (magnesium transporter 1) is a subunit of the oligosaccharide protein complex with thiol-disulfide oxidoreductase activity, supporting the process of N-glycosylation. MAGT1 deficiency was detected in human patients with X-linked immunodeficiency with magnesium defect syndrome and congenital disorders of glycosylation, resulting in decreased cation responses in lymphocytes, thereby inhibiting the immune response against viral infections. Curative hematopoietic stem cell transplantation of patients with X-linked immunodeficiency with magnesium defect causes fatal bleeding and thrombotic complications. METHODS: We studied the role of MAGT1 deficiency in platelet function in relation to arterial thrombosis and hemostasis using several in vitro experimental settings and in vivo models of arterial thrombosis and transient middle cerebral artery occlusion model of ischemic stroke. RESULTS: MAGT1-deficient mice ( Magt1 ^−/y ) displayed accelerated occlusive arterial thrombus formation in vivo, a shortened bleeding time, and profound brain damage upon focal cerebral ischemia. These defects resulted in increased calcium influx and enhanced second wave mediator release, which further reinforced platelet reactivity and aggregation responses. Supplementation of MgCl ₂ or pharmacological blockade of TRPC6 (transient receptor potential cation channel, subfamily C, member 6) channel, but not inhibition of store-operated calcium entry, normalized the aggregation responses of Magt1 ^−/y platelets to the control level. GP (glycoprotein) VI activation of Magt1 ^−/y platelets resulted in hyperphosphorylation of Syk (spleen tyrosine kinase), LAT (linker for activation of T cells), and PLC (phospholipase C) γ2, whereas the inhibitory loop regulated by PKC (protein kinase C) was impaired. A hyperaggregation response to the GPVI agonist was confirmed in human platelets isolated from a MAGT1-deficient (X-linked immunodeficiency with magnesium defect) patient. Haploinsufficiency of TRPC6 in Magt1 ^−/y mice could normalize GPVI signaling, platelet aggregation, and thrombus formation in vivo. CONCLUSIONS: These results suggest that MAGT1 and TRPC6 are functionally linked. Therefore, deficiency or impaired functionality of MAGT1 could be a potential risk factor for arterial thrombosis and stroke.