Hematology Commons^™

Serglycin Controls Megakaryocyte Retention Of Platelet Factor 4 And Influences Megakaryocyte Fate In Bone Marrow, Joshua Lykins, Isabelle C. Becker, Virginia Camacho, Hammodah Rawhi Hammodah Alfar, Joonwoo Park, Joseph Italiano, Sidney W. Whiteheart

Saha Cardiovascular Research Center Faculty Publications

Megakaryocytes (MKs) produce platelets, and similar to other hematopoietic progenitors, they are involved in homeostatic aspects of their bone marrow niche. MKs release and endocytose various factors, such as platelet factor 4 (PF4)/CXCL4. Here, we show that the intra-α-granular proteoglycan, serglycin (SRGN), plays a key role in this process by retaining PF4, and perhaps other factors, during MK maturation. Immature, SRGN–/– MKs released ~80% of their PF4, and conditioned media from these cells negatively affected wild-type MK differentiation in vitro. This was replicated in wild-type MKs by treatment with the polycation surfen, a known inhibitor of glycosaminoglycan (GAG)/protein interactions. In …

Α-Synuclein Is The Major Platelet Isoform But Is Dispensable For Activation, Secretion, And Thrombosis, Alexis N. Smith, Smita Joshi, Harry Chanzu, Hammodah Rawhi Hammodah Alfar, Kanakanagavalli Shravani Prakhya, Sidney W. Whiteheart

Saha Cardiovascular Research Center Faculty Publications

Platelets play many roles in the vasculature ensuring proper hemostasis and maintaining integrity. These roles are facilitated, in part, by cargo molecules released from platelet granules via Soluble NSF Attachment Protein Receptor (SNARE) mediated membrane fusion, which is controlled by several protein-protein interactions. Chaperones have been characterized for t-SNAREs (i.e. Munc18b for Syntaxin-11), but none have been clearly identified for v-SNAREs. α- Synuclein has been proposed as a v-SNARE chaperone which may affect SNARE-complex assembly, fusion pore opening, and thus secretion. Despite its abundance and that it is the only isoform present, α-synuclein’s role in platelet secretion is uncharacterized. In …

Activated Protein C, Protein S, And Tissue Factor Pathway Inhibitor Cooperate To Inhibit Thrombin Activation, Xian Li, Xiaohong Song, Dlovan F. D. Mahmood, Martha M. S. Sim, Sara J. Bidarian, Jeremy P. Wood

Saha Cardiovascular Research Center Faculty Publications

Introduction: Thrombin, the enzyme which converts fibrinogen into a fibrin clot, is produced by the prothrombinase complex, composed of factor Xa (FXa) and factor Va (FVa). Down-regulation of this process is critical, as excess thrombin can lead to life-threatening thrombotic events. FXa and FVa are inhibited by the anticoagulants tissue factor pathway inhibitor alpha (TFPIα) and activated protein C (APC), respectively, and their common cofactor protein S (PS). However, prothrombinase is resistant to either of these inhibitory systems in isolation. Materials and methods: We hypothesized that these anticoagulants function best together, and tested this hypothesis using purified proteins and plasma-based …

Assessing Hip Joint–Related Structure And Patient-Reported Outcomes In People With Marfan Syndrome, Ziyu Zhang, Wen Dai, Wen Zhu, Maya Rodriguez, Hayley Lund, Yuhe Xia, Yiliang Chen, Mary Rau, Ellen Anje Schneider, Mary Beth Graham, Shawn Jobe, Demin Wang, Weiguo Cui, Renren Wen, Sidney W. Whiteheart, Jeremy P. Wood, Roy Silverstein, Jeffery S. Berger, Lisa Baumann Kreuziger, Tessa J. Barrett, Ze Zheng

Saha Cardiovascular Research Center Faculty Publications

Background: Patients with COVID-19 have a higher risk of thrombosis and thromboembolism, but the underlying mechanism(s) remain to be fully elucidated. In patients with COVID-19, high lipoprotein(a) (Lp(a)) is positively associated with the risk of ischemic heart disease. Lp(a), composed of an apoB-containing particle and apolipoprotein(a) (apo(a)), inhibits the key fibrinolytic enzyme, tissue-type plasminogen activator (tPA). However, whether the higher Lp(a) associates with lower tPA activity, the longitudinal changes of these parameters in hospitalized patients with COVID-19, and their correlation with clinical outcomes are unknown.

Objectives: To assess if Lp(a) associates with lower tPA activity in COVID-19 patients, and how …

Platelet Glycogenolysis Is Important For Energy Production And Function, Kanakanagavalli Shravani Prakhya, Hemendra J. Vekaria, Daniёlle M. Coenen, Linda Omali, Joshua Lykins, Smita Joshi, Hammodah Rawhi Hammodah Alfar, Qing Jun Wang, Patrick G. Sullivan, Sidney W. Whiteheart

Saha Cardiovascular Research Center Faculty Publications

Although the presence of glycogen in platelets was established in the 1960s, its importance to specific functions (i.e., activation, secretion, aggregation, and clot contraction) remains unclear. Patients with glycogen storage disease often present with increased bleeding and glycogen phosphorylase (GP) inhibitors, when used as treatments for diabetes, induce bleeding in preclinical studies suggesting some role for this form of glucose in hemostasis. In the present work, we examined how glycogen mobilization affects platelet function using GP inhibitors (CP316819 and CP91149) and a battery of ex vivo assays. Blocking GP activity increased glycogen levels in resting and thrombin-activated platelets and inhibited …

The Complementary Roles Of Vamp-2, -3, And -7 In Platelet Secretion And Function, Smita Joshi, Kanakanagavalli Shravani Prakhya, Alexis N. Smith, Harry Chanzu, Ming Zhang, Sidney W. Whiteheart

Saha Cardiovascular Research Center Faculty Publications

Platelet secretion requires Soluble N-ethylmaleimide Sensitive Attachment Protein Receptors (SNAREs). Vesicle SNAREs/Vesicle-Associated Membrane Proteins (v-SNAREs/ VAMPs) on granules and t-SNAREs in plasma membranes mediate granule release. Platelet VAMP heterogeneity has complicated the assessment of how/if each is used and affects hemostasis. To address the importance of VAMP-7 (V7), we analyzed mice with global deletions of V3 and V7 together or platelet-specific deletions of V2, V3, and global deletion of V7. We measured the kinetics of cargo release, and its effects on three injury models to define the context-specific roles of these VAMPs. Loss of V7 minimally affected dense and α …

Deep Learning, 3d Ultrastructural Analysis Reveals Quantitative Differences In Platelet And Organelle Packing In Covid-19/Sarscov2 Patient-Derived Platelets, Sagar S. Matharu, Cassidy S. Nordmann, Kurtis R. Ottman, Rahul Akkem, Douglas Palumbo, Denzel R. D. Cruz, Kenneth Campbell, Gail Sievert, Jamie L. Sturgill, James Zachary Porterfield, Smita Joshi, Hammodah Rawhi Hammodah Alfar, Chi Peng, Irina D. Pokrovskaya, Jeffrey A. Kamykowski, Jeremy P. Wood, Beth A. Garvy, Maria A. Aronova, Sidney W. Whiteheart, Richard D. Leapman, Brian Storrie

Saha Cardiovascular Research Center Faculty Publications

Platelets contribute to COVID-19 clinical manifestations, of which microclotting in the pulmonary vasculature has been a prominent symptom. To investigate the potential diagnostic contributions of overall platelet morphology and their α-granules and mitochondria to the understanding of platelet hyperactivation and micro-clotting, we undertook a 3D ultrastructural approach. Because differences might be small, we used the high-contrast, high-resolution technique of focused ion beam scanning EM (FIB-SEM) and employed deep learning computational methods to evaluate nearly 600 individual platelets and 30 000 included organelles within three healthy controls and three severely ill COVID-19 patients. Statistical analysis reveals that the α-granule/ mitochondrion-to-plateletvolume ratio …