scholarly journals The human fertilin α gene is non-functional: implications for its proposed role in fertilization

1997 ◽  
Vol 321 (3) ◽  
pp. 577-581 ◽  
Author(s):  
Jennifer A. JURY ◽  
Jan FRAYNE ◽  
Len HALL
Keyword(s):  
Plasma Membrane ◽  
Guinea Pig ◽  
Genetic Recombination ◽  
Surface Membrane ◽  
Membrane Glycoprotein ◽  
Head Region ◽  
Α Subunit ◽  
Functional Implications ◽  
Mammalian Fertilization

In the guinea-pig, the α subunit of the fertilin complex, a heterodimeric surface membrane glycoprotein found on the head region of spermatozoa, has previously been proposed to mediate membrane fusion with the oolemma plasma membrane during fertilization. Here we describe experiments which indicate that the only fertilin α-like gene in humans is an expressed, but non-functional, pseudogene, possibly derived by genetic recombination between the two fertilin α genes found in some primates. This finding clearly raises questions about the importance and/or role of fertilin α in mammalian fertilization.

Spreading of a sperm surface antigen within the plasma membrane of the egg after fertilization in the rat

Development ◽  
1983 ◽  
Vol 75 (1) ◽  
pp. 259-270
Author(s):  
Stephen J. Gaunt
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Guinea Pig ◽  
Surface Antigen ◽  
Plasma Membranes ◽  
Entire Surface ◽  
Sperm Tail ◽  
Sperm Surface ◽  
Sperm Antigens

The rat sperm surface antigen 2D6, located over the entire surface of the spermatozoon, is shown by use of a monoclonal antibody in indirect immunofluorescence experiments to spread laterally over the surface of the egg after fusion of sperm and egg plasma membranes at fertilization. Freshly fertilized eggs, obtained from superovulated rats 14h after hCG injection, showed the 2D6 antigen to have spread in a gradient over a discrete fan-shaped area of the egg surface anterior to the protruding sperm tail. Eggs at a later stage of sperm incorporation, obtained 20 h after hCG injection, snowed that the spread of antigen had extended to cover most or all of their surfaces. By 40 h after hCG injection, the approximate time that fertilized eggs cleaved to form 2-cell embryos, most of the 2D6 antigen had been lost from the cell surface. Fertilized eggs, but not unfertilized eggs or 2-cell embryos, were lysed by 2D6 monoclonal antibody in the presence of guinea pig complement. A model for sperm-egg fusion is presented to account for the observed pattern of spreading shown by the 2D6 antigen. The possible role of sperm antigens on the egg surface is discussed.

scholarly journals Proteolytic processing of a protein involved in sperm-egg fusion correlates with acquisition of fertilization competence.

1990 ◽  
Vol 111 (1) ◽  
pp. 69-78 ◽  
Author(s):  
C P Blobel ◽  
D G Myles ◽  
P Primakoff ◽  
J M White
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Developmental Stages ◽  
Biochemical Properties ◽  
Proteolytic Processing ◽  
Molecular Forms ◽  
Membrane Glycoprotein ◽  
Processing Step

A protein located on the surface of guinea pig sperm (PH-30) has been implicated in the process of sperm-egg fusion (Primakoff, P., H. Hyatt, and J. Tredick-Kline. 1987. J. Cell Biol. 104:141-149). In this paper we have assessed basic biochemical properties of PH-30 and have analyzed the molecular forms of PH-30 present at different stages of sperm maturation. We show the following: (a) PH-30 is an integral membrane glycoprotein; (b) it is composed of two tightly associated and immunologically distinct subunits; (c) both subunits are made as larger precursors; (d) processing of the two subunits occurs at different developmental stages; (e) the final processing step occurs in the region of the epididymis where sperm become fertilization competent; (f) processing can be mimicked in vitro; (g) processing exposes at least two new epitopes on PH-30-one of the newly exposed epitopes is recognized by a fusion-inhibitory monoclonal antibody. These results are discussed in terms of the possible role of PH-30 in mediating fusion with the egg plasma membrane.

scholarly journals Cloning and analysis of monkey fertilin reveals novel α subunit isoforms

1995 ◽  
Vol 307 (3) ◽  
pp. 843-850 ◽  
Author(s):  
A C F Perry ◽  
P M Gichuhi ◽  
R Jones ◽  
L Hall
Keyword(s):  
Macaca Fascicularis ◽  
Surface Membrane ◽  
Beta Subunits ◽  
Cdna Clones ◽  
Head Region ◽  
Α Subunit ◽  
Pcr Products ◽  
Testis Cdna ◽  
High Level ◽  
Mammalian Spermatozoa

The fertilin complex, a heterodimeric surface membrane glycoprotein found on the head region of mammalian spermatozoa, has been reported to mediate membrane fusion with the egg plasma membrane during fertilization. We have employed PCR to generate products corresponding to monkey (Macaca fascicularis) fertilins from testis cDNA. These PCR products have been used to isolate full-length fertilin cDNA clones corresponding to both alpha and beta subunits. Both monkey fertilin alpha and beta cDNAs encode proteins which belong to an expanding family of metalloproteinase-like, disintegrin-like, cysteine-rich, mammalian proteins. Surprisingly, cDNAs for two fertilin alpha isoforms, alpha I and alpha II, were isolated, encoding proteins of 905 and 825 residues respectively. The predicted fertilin alpha isoforms share extensive identity, but differ significantly towards their N- and C-termini, suggesting the possibility of more than one type of fertilin complex in primates. Alignment of monkey alpha and beta fertilins with their respective guinea-pig counterparts suggests a high level of overall structural conservation throughout, whilst providing new insights into the domain function of each.

scholarly journals Glycosylation is essential for biosynthesis of functional gastric H+, K+-ATPase in insect cells

1997 ◽  
Vol 321 (2) ◽  
pp. 419-424 ◽  
Author(s):  
Corné H. W. KLAASSEN ◽  
Jack A. M. FRANSEN ◽  
Herman G. P. SWARTS ◽  
Jan Joep H. H. M. De PONT
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Functional Properties ◽  
Insect Cells ◽  
Expression Level ◽  
Α Subunit ◽  
Atpase Subunits ◽  
Glycoprotein Processing ◽  
Α Subunits

The role of N-linked glycosylation in the functional properties of gastric H+,K+-ATPase has been examined with tunicamycin and 1-deoxymannojirimycin, inhibitors of glycoprotein biosynthesis and glycoprotein processing respectively. Tunicamycin completely abolished both K+-stimulated and 3-(cyanomethyl)-2-methyl-8-(phenylmethoxy)-imidazo[1,2a]pyridine (SCH 28080)-sensitive ATPase activity and SCH 28080-sensitive phosphorylation capacity. The expression level of both H+,K+-ATPase subunits remained unaffected. 1-Deoxymannojirimycin clearly affected the structure of the N-linked oligosaccharide moieties without affecting specific phosphorylation capacity. Purification of the functional recombinant enzyme from non-functional H+,K+-ATPase subunits coincided with purification of glycosylated α-subunits and not of non-glycosylated α-subunits. Transport of the H+,K+-ATPase α-subunit to the plasma membrane but not its ability to assemble with the α-subunit depended on N-glycosylation events. We conclude that the acquisition, but not the exact structure, of N-linked oligosaccharide moieties, is essential for biosynthesis of functional gastric H+,K+-ATPase in insect cells.

Intrarenal suppression of angiotensin II type 1 receptor binding molecule in angiotensin II-infused mice

2010 ◽  
Vol 299 (5) ◽  
pp. F991-F1003 ◽  
Author(s):  
Hiromichi Wakui ◽  
Kouichi Tamura ◽  
Miyuki Matsuda ◽  
Yunzhe Bai ◽  
Toru Dejima ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Angiotensin Ii ◽  
Ang Ii ◽  
Significant Suppression ◽  
Outer Medulla ◽  
Α Subunit ◽  
Angiotensinogen Gene

ATRAP [ANG II type 1 receptor (AT1R)-associated protein] is a molecule which directly interacts with AT1R and inhibits AT1R signaling. The aim of this study was to examine the effects of continuous ANG II infusion on the intrarenal expression and distribution of ATRAP and to determine the role of AT1R signaling in mediating these effects. C57BL/6 male mice were subjected to vehicle or ANG II infusions at doses of 200, 1,000, or 2,500 ng·kg−1·min−1 for 14 days. ANG II infusion caused significant suppression of ATRAP expression in the kidney but did not affect ATRAP expression in the testis or liver. Although only the highest ANG II dose (2,500 ng·kg−1·min−1) provoked renal pathological responses, such as an increase in the mRNA expression of angiotensinogen and the α-subunit of the epithelial sodium channel, ANG II-induced decreases in ATRAP were observed even at the lowest dose (200 ng·kg−1·min−1), particularly in the outer medulla of the kidney, based on immunohistochemical staining and Western blot analysis. The decrease in renal ATRAP expression by ANG II infusion was prevented by treatment with the AT1R-specific blocker olmesartan. In addition, the ANG II-mediated decrease in renal ATRAP expression through AT1R signaling occurred without an ANG II-induced decrease in plasma membrane AT1R expression in the kidney. On the other hand, a transgenic model increase in renal ATRAP expression beyond baseline was accompanied by a constitutive reduction of renal plasma membrane AT1R expression and by the promotion of renal AT1R internalization as well as the decreased induction of angiotensinogen gene expression in response to ANG II. These results suggest that the plasma membrane AT1R level in the kidney is modulated by intrarenal ATRAP expression under physiological and pathophysiological conditions in vivo.

pH-induced changes in calcium: functional consequences and mechanisms of action in guinea pig portal vein

2002 ◽  
Vol 283 (6) ◽  
pp. H2518-H2526 ◽  
Author(s):  
R. D. Smith ◽  
D. A. Eisner ◽  
Susan Wray
Keyword(s):  
Guinea Pig ◽  
Portal Vein ◽  
Surface Membrane ◽  
Mechanisms Of Action ◽  
High K ◽  
Effects Of Ph ◽  
Functional Consequences ◽  
Induced Changes ◽  
Intracellular Alkalinization

The effects of changing extracellular (pHo) and intracellular pH (pHi) on force and the mechanisms involved in the guinea pig portal vein were investigated to better understand the control of tone in this vessel. When pHo was altered, the effects on force and calcium were the same irrespective of whether force had been produced spontaneously by high-K depolarization or by norepinephrine; alkalinization increased tone, and acidification reduced it. Because pHo changes also lead to changes in pHi, we determined whether the effects on force could be explained by these induced pHi changes. It was found, however, that only with spontaneous activity did intracellular alkalinization increase force. In depolarized preparations, force was decreased, and, with norepinephrine, force was initially decreased and then increased. Thus the effects of pHo cannot be explained solely by changes in pHi. The role of the sarcoplasmic reticulum (SR) and surface membrane Ca2+-ATPase on the mechanism were investigated and shown not to be involved. Therefore, it is concluded that both pHo and pHi can have powerful modulatory effects on portal vein tone, that these effects are not identical, and that they are likely to be due to effects of pH on ion channels rather than the SR or plasma membrane Ca2+-ATPase.

Role of neuronal Ca2+-sensor proteins in Golgi–cell-surface membrane traffic

2010 ◽  
Vol 38 (1) ◽  
pp. 177-180 ◽  
Author(s):  
Marina Mikhaylova ◽  
Pasham Parameshwar Reddy ◽  
Michael R. Kreutz
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Surface Membrane ◽  
Golgi Membrane ◽  
Golgi Cell ◽  
Local Synthesis ◽  
Late Step ◽  
Sensor Proteins ◽  
Golgi Network

The regulated local synthesis of PtdIns4P and PtdIns(4,5)P2 is crucial for TGN (trans-Golgi network)–plasma membrane trafficking. The activity of PI4Kβ (phosphoinositide 4-kinase IIIβ) at the Golgi membrane is a first mandatory step in this process. In addition to PI4Kβ activity, elevated Ca2+ levels are also needed for the exit of vesicles from the TGN. The reason for this Ca2+ requirement is at present unclear. In the present review, we discuss the role of neuronal Ca2+-sensor proteins in the regulation of PI4Kβ and suggest that this regulation might impose a need for elevated Ca2+ levels for a late step of vesicle assembly.

Role of the Cilia Membrane in Control of Microtubule Sliding

1980 ◽  
Vol 38 ◽  
pp. 612-615
Author(s):  
Edna S. Kaneshiro
Keyword(s):  
Control Mechanism ◽  
Beat Frequency ◽  
Surface Membrane ◽  
Ciliary Membrane ◽  
Ciliary Beating ◽  
Ciliary Reversal ◽  
Voltage Dependent ◽  
Reversal Mechanism ◽  
And Function

It is currently believed that ciliary beating results from microtubule sliding which is restricted in regions to cause bending. Cilia beat can be modified to bring about changes in beat frequency, cessation of beat and reversal in beat direction. In ciliated protozoans these modifications which determine swimming behavior have been shown to be related to intracellular (intraciliary) Ca2+ concentrations. The Ca2+ levels are in turn governed by the surface ciliary membrane which exhibits increased Ca2+ conductance (permeability) in response to depolarization. Mutants with altered behaviors have been isolated. Pawn mutants fail to exhibit reversal of the effective stroke of ciliary beat and therefore cannot swim backward. They lack the increased inward Ca2+ current in response to depolarizing stimuli. Both normal and pawn Paramecium made leaky to Ca2+ by Triton extrac¬tion of the surface membrane exhibit backward swimming only in reactivating solutions containing greater than IO-6 M Ca2+ Thus in pawns the ciliary reversal mechanism itself is left operational and only the control mechanism at the membrane is affected. The topographic location of voltage-dependent Ca2+ channels has been identified as a component of the ciliary mem¬brane since the inward Ca2+ conductance response is eliminated by deciliation and the return of the response occurs during cilia regeneration. Since the ciliary membrane has been impli¬cated in the control of Ca2+ levels in the cilium and therefore is the site of at least one kind of control of microtubule sliding, we have focused our attention on understanding the structure and function of the membrane.

Differential Ability of Agonists to Express Distinct Pools of Fibrinogen (Gpllb/llla) Receptors which Can Mediate the Aggregation of Human Platelets

1989 ◽  
Vol 62 (03) ◽  
pp. 955-961 ◽  
Author(s):  
Ian S Watts ◽  
Rebecca J Keery ◽  
Philip Lumley
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Surface Membrane ◽  
Blood Platelet ◽  
Human Platelets ◽  
Membrane Glycoprotein ◽  
Platelet Surface ◽  
Human Platelet Aggregation ◽  
Differential Ability ◽  
Blood Platelet Aggregation

SummaryWe have investigated the effect of two procedures that modify human platelet surface membrane glycoprotein (Gp) IIb and IIIa complexes upon whole blood platelet aggregation to a range of agonists. (A) Irreversible disruption of complexes by temporary (30 min) Ca2+-deprivation with EGTA at 37° C. (B) Binding of a monoclonal antibody M148 to the complex. EGTA exposure abolished aggregation to ADP, adrenaline and PAF. In contrast, full aggregation curves to collagen and U-46619 could still be established. EGTA exposure reduced M148 binding to platelets by 80%. Excess M148 abolished aggregation to ADP, PAF, collagen and U-46619. However, upon removal of unbound antibody from platelets full aggregation curves to collagen and U-46619 but not to ADP and PAF could be re-established. Thus human platelet aggregation to ADP, PAF and adrenaline appears absolutely dependent upon surface membrane GpIIb/IIIa complexes. In contrast, collagen and U-46619 cause expression of an additional distinct pool of Gp complexes inaccessible to EGTA and M148 in unstimulated platelets which is intimately involved in aggregation to these agonists.

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