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Sperm Capacitation2
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- 2. What is capacitation? •It is a process that allows the acrosome reaction to occur, So the sperm can penetrate the zona pellucida of the oocyte. • The physiological changes that confer on the sperm the ability to fertilize are called Capacitation.
- 3. Introduction • After leavingthe testis, mammalian spermatozoa are morphologically differentiated but have acquired neither progressive motility nor the ability to fertilize a metaphase II arrested egg. • During epididymal transit, sperm acquire the ability to move progressively; but they are still fertilization incompetent.
- 4. Int.Cont. • Fertilization capacityis gained after residence in the female tract for a finite time. • Capacitation is also correlated with changes in sperm motility patterns, designated as sperm hyperactivation. • Capacitation causes head changes (acrosome reaction) and tail changes (motility changes).
- 5. Capacitation consists ofat least two components: 1- An initial membrane alteration, that allows spermatozoa to undergo the second phase, which is the fusion of plasma membrane with outer acrosomal membrane. -The first phase is referred to as capacitation. - The second phase is referred to as acrosome reaction(AR).
- 8. Original Models ofCapacitation Epididymal Capacitated Female Tract + Ejaculated Seminal Plasma + Decapacitation Factors
- 9. Sperm tail changesafter capacitation
- 10. What cause spermcapacitation? • In vivo the oviduct and uterus fluids capacitate the spermatozoa in different animals. • In vitro, both caudal or ejaculated sperm capacitate when incubate under a variety of conditions in defined madia.
- 11. In Vitro Spermcapacitation The sperm cell is programmed to undergo capacitation when it is incubated in the appropriate medium. 1-Role of media constituents. - Serum albumin. - Calcium. - Bicarbonate. 2- Effectors and intracellular messengers. - Cyclic AMP metabolism. - Protein tyrosine phosphrylation.
- 12. In Vitro capacitationCont. - pH. - Membrane potential. - Free radicals. - Heparin. - Glucose.
- 13. Ejaculated spermatozoa • Containdecapacitated agent.
- 14. Initial Events inCapacitation • Decapacitation factor removal – Time dependent – Induced by binding of a capacitating agent • Glycosaminoglycans - heparin or heparan sulfate – Components of extracellular matrix of uterine and oviduct cells – Induced by cholesterol removal • Acceptor is albumin – Sequence not clear
- 15. Ejaculated Sperm D F PlasmaMembrane Cytoplasm Nucleus Acrosome
- 16. D F Cytoplasm Nucleus Acrosome GAG Cholesterol Chol-Acceptor D F DF D F D F Heparin Time? Albumin
- 19. Role of mediaconstituents -Serum albumin ( usually bovine serum albumin) BSA. . BAS during in vitro capacitation remove cholestrol from sperm plasma membrane. BSA A1 BSA-chol. Sperm plasma membrane Cholestrol efflux
- 20. Role of mediaconstituents -Calcium:increase in intracellular Ca during capacitation. Capacitate sperm with heparin requires extracellular calcium. When medium Ca decline the time required for capacitation increases. Sperm plasma membrane Cholesterol efflux BSA BSA-chol. Ca Ca A2 A1
- 21. Ejaculated Sperm D F PlasmaMembrane Cytoplasm Nucleus Acrosome
- 22. D F Cytoplasm Nucleus Acrosome GAG Cholesterol Chol-Acceptor D F DF D F D F Heparin Time? Albumin
- 26. ATP ADP (+( Decapacitation Factors (Seminal Plasma) DF Ca2+ •Ejaculated Sperm •>> Active Ca2+ ATPase •Removal DF >> Decreased Ca2+-ATPase Low Ca (-) Heparin and Cholesterol Removal Ca2+ Ca2+ Na+ Ca2+ H+ Increasing Ca
- 27. Role of mediaconstituents -Bicarbonate:Transmembrane movement of HCO3 responsible for increase in intracellular pH that is observed during capacitation. SPM Cholesterol efflux BSA BSA-chol. A1 Ca Ca A2+ HCO3 HCO3 A3 AC + +
- 28. Intracellular second messengers •Intracellular messenger mediating capacitation will be considered from two respective. - The regulatory system that appear to be common among different species. - The regulatory process that may be unique to one or more species.
- 29. Intracellular second messenger cont. -CyclicAMP metabolism:The protein kinase A (PK-A) activity increases during sperm capacitation as a result of elevation intracellular cAMP. - The mode of regulation of cAMP metabolism during sperm capacitation may be integrated with changes in Ca and HCO3 movement.
- 30. S.P.M. Cholesterol efflux BSA A1 BSA-chol. + HCO3 HCO3 A3 Ca A2 Ca ++ AC cAMP PDE + PK-A 5`AMP Role of cAMP in sperm capacitation B1
- 31. - Protein tyrosinephosphorylation • Protein tyrosine phosphorylation mediates a variety of cellular function . • The increase in protein tyrosine phosphorylation is dependent on the presence of BSA, Ca and NaHCO3 in the medium. • The role of protein tyrosine phosphorylation in sperm capacitation is regulated through a PK- A.
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- 33. Intracellular pH • ThepH increase during sperm capacitation. • Increase pH during bovine sperm capacitation by heparin.
- 34. Cholesterol efflux BSA A1 BSA-chol. + HCO3 HCO3 A3 Ca A2 Ca + + AC cAMP PDE + PK-A PTK + + - Ptyr-Ptase - Proteintyrosine phosphrylation B1 B2 5`AMP S.P.M. Recheparin Ca cAMP pH B3
- 35. - Membrane potential •Capacitation is accompanied by the hyperpolarization of the sperm plasma membrane. • Membrane hyperpolarization is due to an enhanced k permeability.
- 36. Cholesterol efflux BSA A1 BSA-chol. + HCO3 HCO3 A3 Ca A2 Ca ++ AC cAMP PDE + PK-A PTK + + - - B1 B2 Rec Ca cAMP pH B3 5`AMP Ptyr-Ptase Protein tyrosine phosphrylation S.P.M. heparin KK hyperpolarization + B4 Capacitation
- 37. -Free radicals • Thefree radicals has a role in sperm lipid peroxidation and sperm viability. • Superoxide anion cause capacitation and hyperactivationof the spermatozoa. • Reactive oxygen regulate protein tyrosine phosphorelation of several protein.
- 38. Cholesterol efflux BSA A1 BSA-chol. + HCO3 HCO3 A3 Ca A2 Ca + + AC cAMP PDE + PK-A PTK + + - - B1 B2 Rec Ca cAMP pH B3 heparin KK hyperpolarization + B4 Capacitation 5`AMP Proteintyrosine phosphrylation Ptyr-Ptase S.P.M. O2 NO B5a B5b
- 39. -Heparin • Bovine invitro sperm capacitation can be accomplished in media containing heparin. • The active capacitating agent in the oviduct fluid is though to be a heparin-like glycosaminoglycan. • The glycosaminoglycan may promote capacitation by binding to and removing seminal plasma protein. • Heparin increases cAMP synthesis,elevate pH and regulate the capacitation-associated changes.
- 41. Ejaculated Sperm D F PlasmaMembrane Cytoplasm Nucleus AcrosomeAcrosome
- 42. D F Cytoplasm Nucleus AcrosomeAcrosome GAG Cholesterol Chol-Acceptor D F DF D F D F Heparin Time? Albumin
- 43. Cholesterol efflux BSA A1 BSA-chol. + HCO3 HCO3 A3 Ca A2 Ca ++ AC cAMP PDE + PK-A PTK + + - - B1 B2 Rec Ca cAMP pH B3 heparin KK hyperpolarization + B4 Capacitation 5`AMP Protein tyrosine phosphrylation Ptyr-Ptase O2 NO B5a B5b S.P.M. + B6
- 44. -Glucose • Glucose hasinhibitory or stimulatory actions on capacitation is controversial and is species dependent. • In bovine glucose inhibits heparin-induced capacitation in vitro. • Capacitation medium for mouse sperm, which contains glucose has no inhibatory effects .
- 45. Cholesterol efflux BSA A1 BSA-chol. + HCO3 HCO3 A3 Ca A2 Ca ++ AC cAMP PDE + PK-A PTK + + - - B1 B2 Rec Ca cAMP pH B3 heparin KK hyperpolarization + B4 Capacitation 5`AMP Protein tyrosine phosphrylation Ptyr-Ptase O2 NO B5a B5b + B6 S.P.M. glucose Gluc. pyruvate 2ATP 2NADH 2H - B7
- 46. The Acrosome Reaction PlasmaMembrane Acrosome Fused Plasma Membrane and Outer Acrosomal Membrane Nucleus Acrosin Hyaluronidase