scholarly journals The Functional Role of Platelet-Activating Factor in Spermatozoa Physiology

2021 ◽  
Keyword(s):  
Functional Role ◽  
Platelet Activating Factor ◽  
Cell Types ◽  
Sperm Function ◽  
Male Factor Infertility ◽  
Male Factor ◽  
Synthesis Mechanism ◽  
Numerous Cell ◽  
G Protein Coupled

Platelet-activating factor (alkylacetylglycerolphosphocholine; PAF) is a potent signaling phospholipid which has been found in numerous cell types in every physiological system studied to date. In reproduction, PAF is found to have a variety of roles, for example: in ovulation, sperm function, and early preimplantation development. The goal of this mini review is to highlight PAF’s synthesis, mechanism of action and its functional role in sperm physiology. PAF functions via a G protein coupled receptor mediated pathway, which ultimately increases intracellular calcium levels to enhance sperm motility required for fertilization. Exogenous PAF was also found to increase fertilization potential of spermatozoa in cases of non-male factor infertility. Finally, the mini review explores various lifestyle factors that could potentially affect PAF levels and fertility.

Role of the teneurins, teneurin C-terminal associated peptides (TCAP) in reproduction: clinical perspectives

2015 ◽  
Vol 24 (2) ◽  
Author(s):  
David A. Lovejoy ◽  
Téa Pavlović
Keyword(s):  
Cell Types ◽  
Reproductive Physiology ◽  
Corticotropin Releasing Factor ◽  
Peptide Sequence ◽  
Gene Duplications ◽  
Terminal Exon ◽  
Numerous Cell ◽  
Multicellular Organisms ◽  
G Protein Coupled

AbstractIn humans, the teneurin gene family consists of four highly conserved paralogous genes that are the result of early vertebrate gene duplications arising from a gene introduced into multicellular organisms from a bacterial ancestor. In vertebrates and humans, the teneurins have become integrated into a number of critical physiological systems including several aspects of reproductive physiology. Structurally complex, these genes possess a sequence in their terminal exon that encodes for a bioactive peptide sequence termed the ‘teneurin C-terminal associated peptide’ (TCAP). The teneurin/TCAP protein forms an intercellular adhesive unit with its receptor, latrophilin, an Adhesion family G-protein coupled receptor. It is present in numerous cell types and has been implicated in gamete migration and gonadal morphology. Moreover, TCAP is highly effective at reducing the corticotropin-releasing factor (CRF) stress response. As a result, TCAP may also play a role in regulating the stress-associated inhibition of reproduction. In addition, the teneurins and TCAP have been implicated in tumorigenesis associated with reproductive tissues. Therefore, the teneurin/TCAP system may offer clinicians a novel biomarker system upon which to diagnose some reproductive pathologies.

scholarly journals Role of GRK6 in the Regulation of Platelet Activation through Selective G Protein-Coupled Receptor (GPCR) Desensitization

2020 ◽  
Vol 21 (11) ◽  
pp. 3932 ◽  
Author(s):  
Preeti Kumari Chaudhary ◽  
Sanggu Kim ◽  
Youngheun Jee ◽  
Seung-Hun Lee ◽  
Kyung-Mee Park ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
G Protein ◽  
Platelet Activation ◽  
Functional Role ◽  
Thrombus Formation ◽  
Receptor Activation ◽  
G Protein Coupled ◽  
Gpcr Desensitization ◽  
Stimulation Of

Platelet G protein-coupled receptors (GPCRs) regulate platelet function by mediating the response to various agonists, including adenosine diphosphate (ADP), thromboxane A2, and thrombin. Although GPCR kinases (GRKs) are considered to have the crucial roles in most GPCR functions, little is known regarding the regulation of GPCR signaling and mechanisms of GPCR desensitization by GRKs in platelets. In this study, we investigated the functional role of GRK6 and the molecular basis for regulation of specific GPCR desensitization by GRK6 in platelets. We used GRK6 knockout mice to evaluate the functional role of GRK6 in platelet activation. Platelet aggregation, dense- and α-granule secretion, and fibrinogen receptor activation induced by 2-MeSADP, U46619, thrombin, and AYPGKF were significantly potentiated in GRK6−/− platelets compared to the wild-type (WT) platelets. However, collagen-related peptide (CRP)-induced platelet aggregation and secretion were not affected in GRK6−/− platelets. Interestingly, platelet aggregation induced by co-stimulation of serotonin and epinephrine which activate Gq-coupled 5HT2A and Gz-coupled α2A adrenergic receptors, respectively, was not affected in GRK6−/− platelets, suggesting that GRK6 was involved in specific GPCR regulation. In addition, platelet aggregation in response to the second challenge of ADP and AYPGKF was restored in GRK6−/− platelets whereas re-stimulation of the agonist failed to induce aggregation in WT platelets, indicating that GRK6 contributed to P2Y1, P2Y12, and PAR4 receptor desensitization. Furthermore, 2-MeSADP-induced Akt phosphorylation and AYPGKF-induced Akt, extracellular signal-related kinase (ERK), and protein kinase Cδ (PKCδ) phosphorylation were significantly potentiated in GRK6−/− platelets. Finally, GRK6−/− mice exhibited an enhanced and stable thrombus formation after FeCl3 injury to the carotid artery and shorter tail bleeding times, indicating that GRK6−/− mice were more susceptible to thrombosis and hemostasis. We conclude that GRK6 plays an important role in regulating platelet functional responses and thrombus formation through selective GPCR desensitization.

scholarly journals Essential Role of Sperm-Specific PLC-Zeta in Egg Activation and Male Factor Infertility: An Update

2020 ◽  
Vol 8 ◽  
Author(s):  
Alaaeldin Saleh ◽  
Junaid Kashir ◽  
Angelos Thanassoulas ◽  
Bared Safieh-Garabedian ◽  
F. Anthony Lai ◽  
...  
Keyword(s):  
Essential Role ◽  
Egg Activation ◽  
Male Factor Infertility ◽  
Male Factor

Autoradiographic analysis and regulation of angiotensin receptor subtypes AT4, AT1, and AT(1—7) in the kidney

2001 ◽  
Vol 281 (5) ◽  
pp. F936-F947 ◽  
Author(s):  
Rajash K. Handa ◽  
Shelly E. Handa ◽  
Monica K. S. Elgemark
Keyword(s):  
Cell Types ◽  
Receptor Subtypes ◽  
Receptor Density ◽  
Angiotensin Receptor ◽  
Puromycin Aminonucleoside ◽  
Water Diuresis ◽  
Receptor System ◽  
Numerous Cell ◽  
Autoradiographic Analysis

Receptor autoradiography revealed that angiotensin AT4 receptors were abundantly expressed in normal mammalian (mouse, rat, gerbil, guinea pig, rabbit) and avian (sparrow, chicken, turkey) kidneys and were more extensively distributed than previously reported (including proximal and distal segments of the nephron, interstitium, renal artery, vein, and ureter). Angiotensin AT4 receptors were generally found to be more abundant than angiotensin AT1 receptors in mammalian kidneys, whereas angiotensin AT(1—7) receptors were not detected in either mammalian or avian kidneys. Rats subjected to various chronic treatments were found to preferentially decrease kidney AT4 receptor density (furosemide, puromycin aminonucleoside, nitro-l-arginine methyl ester), decrease kidney AT1 receptor density (bilateral ureteral obstruction), or increase kidney AT1 receptor distribution in the inner medulla (water diuresis). These results indicate that the AT4 receptor can be expressed in numerous cell types within the normal kidney of several species. Furthermore, several models of renal dysfunction and injury have been identified that selectively alter kidney AT4 density and may potentially aid in elucidating the role of this novel angiotensin receptor system in renal function.

scholarly journals Anaphylactic shock depends on endothelial Gq/G11

2009 ◽  
Vol 206 (2) ◽  
pp. 411-420 ◽  
Author(s):  
Hanna Korhonen ◽  
Beate Fisslthaler ◽  
Alexandra Moers ◽  
Angela Wirth ◽  
Daniel Habermehl ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Anaphylactic Shock ◽  
Platelet Activating Factor ◽  
Severe Allergic Reaction ◽  
Downstream Signaling ◽  
Systemic Anaphylaxis ◽  
Multiple Organs ◽  
Nitric Oxide Formation ◽  
G Protein Coupled

Anaphylactic shock is a severe allergic reaction involving multiple organs including the bronchial and cardiovascular system. Most anaphylactic mediators, like platelet-activating factor (PAF), histamine, and others, act through G protein–coupled receptors, which are linked to the heterotrimeric G proteins Gq/G11, G12/G13, and Gi. The role of downstream signaling pathways activated by anaphylactic mediators in defined organs during anaphylactic reactions is largely unknown. Using genetic mouse models that allow for the conditional abrogation of Gq/G11- and G12/G13-mediated signaling pathways by inducible Cre/loxP-mediated mutagenesis in endothelial cells (ECs), we show that Gq/G11-mediated signaling in ECs is required for the opening of the endothelial barrier and the stimulation of nitric oxide formation by various inflammatory mediators as well as by local anaphylaxis. The systemic effects of anaphylactic mediators like histamine and PAF, but not of bacterial lipopolysaccharide (LPS), are blunted in mice with endothelial Gαq/Gα11 deficiency. Mice with endothelium-specific Gαq/Gα11 deficiency, but not with Gα12/Gα13 deficiency, are protected against the fatal consequences of passive and active systemic anaphylaxis. This identifies endothelial Gq/G11-mediated signaling as a critical mediator of fatal systemic anaphylaxis and, hence, as a potential new target to prevent or treat anaphylactic reactions.

scholarly journals Immunomodulation by Gut Microbiota: Role of Toll-Like Receptor Expressed by T Cells

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Mariagrazia Valentini ◽  
Alessia Piermattei ◽  
Gabriele Di Sante ◽  
Giuseppe Migliara ◽  
Giovanni Delogu ◽  
...  
Keyword(s):  
T Cells ◽  
Immune System ◽  
Gut Microbiota ◽  
Cell Types ◽  
Mutual Regulation ◽  
Close Relationship ◽  
Numerous Cell ◽  
Specific Receptors ◽  
And Function

A close relationship exists between gut microbiota and immune responses. An imbalance of this relationship can determine local and systemic immune diseases. In fact the immune system plays an essential role in maintaining the homeostasis with the microbiota that normally resides in the gut, while, at the same time, the gut microbiota influences the immune system, modulating number and function of effector and regulatory T cells. To achieve this aim, mutual regulation between immune system and microbiota is achieved through several mechanisms, including the engagement of toll-like receptors (TLRs), pathogen-specific receptors expressed on numerous cell types. TLRs are able to recognize ligands from commensal or pathogen microbiota to maintain the tolerance or trigger the immune response. In this review, we summarize the latest evidences about the role of TLRs expressed in adaptive T cells, to understand how the immune system promotes intestinal homeostasis, fights invasion by pathogens, and is modulated by the intestinal microbiota.

scholarly journals Differential phosphorylation signals control endocytosis of GPR15

2017 ◽  
Vol 28 (17) ◽  
pp. 2267-2281 ◽  
Author(s):  
Yukari Okamoto ◽  
Sojin Shikano
Keyword(s):  
Surface Density ◽  
Functional Role ◽  
Control Cell ◽  
Phosphorylation Site ◽  
Hek293 Cells ◽  
C Terminus ◽  
Differential Phosphorylation ◽  
G Protein Coupled

GPR15 is an orphan G protein–coupled receptor (GPCR) that serves for an HIV coreceptor and was also recently found as a novel homing receptor for T-cells implicated in colitis. We show that GPR15 undergoes a constitutive endocytosis in the absence of ligand. The endocytosis was clathrin dependent and partially dependent on β-arrestin in HEK293 cells, and nearly half of the internalized GPR15 receptors were recycled to the plasma membrane. An Ala mutation of the distal C-terminal Arg-354 or Ser-357, which forms a consensus phosphorylation site for basophilic kinases, markedly reduced the endocytosis, whereas phosphomimetic mutation of Ser-357 to Asp did not. Ser-357 was phosphorylated in vitro by multiple kinases, including PKA and PKC, and pharmacological activation of these kinases enhanced both phosphorylation of Ser-357 and endocytosis of GPR15. These results suggested that Ser-357 phosphorylation critically controls the ligand-independent endocytosis of GPR15. The functional role of Ser-357 in endocytosis was distinct from that of a conserved Ser/Thr cluster in the more proximal C-terminus, which was responsible for the β-arrestin– and GPCR kinase–dependent endocytosis of GPR15. Thus phosphorylation signals may differentially control cell surface density of GPR15 through endocytosis.

scholarly journals Neutrophils Stimulated with a Variety of Chemoattractants Exhibit Rapid Activation of p21-Activated Kinases (Paks): Separate Signals Are Required for Activation and Inactivation of Paks

1998 ◽  
Vol 18 (12) ◽  
pp. 7130-7138 ◽  
Author(s):  
RiYun Huang ◽  
Jian P. Lian ◽  
Dwight Robinson ◽  
John A. Badwey
Keyword(s):  
G Proteins ◽  
Platelet Activating Factor ◽  
Cell Types ◽  
Mitogen Activated Protein Kinase ◽  
Transient Activation ◽  
Anaphylatoxin C5a ◽  
Mitogen Activated Protein ◽  
Fmlp Receptor ◽  
Rapid Activation ◽  
G Protein Coupled

ABSTRACT Activation of the p21-activated protein kinases (Paks) was compared in neutrophils stimulated with a wide variety of agonists that bind to receptors coupled to heterotrimeric G proteins. Neutrophils stimulated with sulfatide, a ligand for the L-selectin receptor, or the chemoattractant fMet-Leu-Phe (fMLP), platelet-activating factor, leukotriene B4, interleukin-8, or the chemokine RANTES exhibited a rapid and transient activation of the 63- and 69-kDa Paks. These kinases exhibited maximal activation with each of these agonists within 15 s followed by significant inactivation at 3 min. In contrast, neutrophils treated with the chemoattractant and anaphylatoxin C5a exhibited a prolonged activation (>15 min) of these Paks even though the receptor for this ligand may activate the same overall population of complex G proteins as the fMLP receptor. Addition of fMLP to neutrophils already stimulated with C5a resulted in the inactivation of the 63- and 69-kDa Paks. Optimal activation of Paks could be observed at concentrations of these agonists that elicited only shape changes and chemotaxis in neutrophils. While all of the agonists listed above triggered quantitatively similar activation of the 63- and 69-kDa Paks, fMLP was far superior to the other stimuli in triggering activation of the c-Jun N-terminal kinase (JNK) and the p38 mitogen-activated protein kinase (MAPK). These data indicate that separate signals are required for activation and inactivation of Paks and that, in contrast to other cell types, activated Pak does not trigger activation of JNK or p38-MAPK in neutrophils. These results are consistent with the recent hypothesis that G-protein-coupled receptors may initiate signals independent of those transmitted by the α and βγ subunits of complex G proteins.

Sign in / Sign up

Export Citation Format

Share Document