The Adaptor Protein Swiprosin-1/EFhd2 Is Dispensable for Platelet Function in Mice

Abstract

BackgroundPlatelets are anuclear cell fragments derived from bone marrow megakaryocytes that safeguard vascular integrity, but may also cause pathological vessel occlusion. Reorganizations of the platelet cytoskeleton and agonist-induced intracellular Ca2+-mobilization are crucial for platelet hemostatic function. EF-hand domain containing 2 (EFhd2, Swiprosin-1) is a Ca2+-binding cytoskeletal adaptor protein involved in actin remodeling in different cell types, but its function in platelets is unknown.ObjectiveBased on the described functions of EFhd2 in immune cells, we tested the hypothesis that EFhd2 is a crucial adaptor protein for platelet function acting as a regulator of Ca2+-mobilization and cytoskeletal rearrangements.Methods and ResultsWe generated EFhd2-deficient mice and analyzed their platelets in vitro and in vivo. Efhd2-/- mice displayed normal platelet count and size, exhibited an unaltered in vivo life span and showed normal Ca2+-mobilization and activation/aggregation responses to classic agonists. Interestingly, upon stimulation of the immunoreceptor tyrosine-based activation motif-coupled receptor glycoprotein (GP) VI, Efhd2-/- platelets showed a slightly increased coagulant activity. Furthermore, absence of EFhd2 had no significant impact on integrin-mediated clot retraction, actomyosin rearrangements and spreading of activated platelets on fibrinogen. In vivo EFhd2-deficiency resulted in unaltered hemostatic function and unaffected arterial thrombus formation.ConclusionThese results show that EFhd2 is not essential for platelet function in mice indicating that other cytoskeletal adaptors may functionally compensate its loss.

Low level of swiprosin-1/EFhd2 in vestibular nuclei of spontaneously hypersensitive motion sickness mice

“…Swiprosin-1 was first identified in human lymphocytes, predominantly in CD 8+ lymphocytes 26 and later in immature, resting or activated B cells 27 28 , mast cells 29 30 , human peripheral blood mononuclear cells 31 and mouse platelets 32 . Swiprosin-1 was also found in non-lymphoid tissue, especially in the brain 33 34 35 .…”

Genetic Nicotinamide N-Methyltransferase (Nnmt) Deficiency in Male Mice Improves Insulin Sensitivity in Diet-Induced Obesity but Does Not Affect Glucose Tolerance

“…Western blot of epididymal WAT (eWAT) using Total OXPHOS WB-Antibody-Cocktail (ab110413; Abcam), rabbitanti-mouse NNMT (ARP42281_T100; Aviva Systems Biology), rabbit-anti-mouse a-tubulin (2144; NEB), and horseradish peroxidase-anti-rabbit IgG (7074; Cell Signaling Technology) for detection was conducted as described previously (18,19). Optical density (OD) was quantified by ImageJ (20).…”

Swiprosin‐1: Its Expression and Diverse Biological Functions

“…Swiprosin‐1 deficient mice platelets showed normal Ca 2+ store release when stimulated with major platelet agonists like CRP and thrombin [Morowski et al, ]. Further, a hydrophobicity plot of murine swiprosin‐1 (Q9D8Y0) according to Kyte and Doolittle reveals that EF‐hand 1 (EF1) of swiprosin‐1 is more hydrophilic than EF‐hand 2 (EF2).…”