The role of ezrin-associated protein network in human sperm capacitation.
Membrane modifications in sperm cells represent a key step in sperm capacitation; however, the molecular basis of these modifications is not fully understood. Ezrin is the best-studied member of the ezrin/radixin/merlin family. As a cross-linker between the cortical cytoskeleton and plasma membrane proteins, ezrin contributes to remodeling of the membrane surface structure. Furthermore, activated ezrin and the Rho dissociation inhibitor, RhoGDI, promote the formation of cortical cytoskeleton-polymerized actin through Rho activation. Thus, ezrin, actin, RhoGDI, Rho and plasma membrane proteins form a complicated network in vivo, which contributes to the assembly of the structure of the membrane surface. Previously, we showed that ezrin and RhoGDI1 are expressed in human testes. Thus, we sought to determine whether the ezrin-RhoGDI1-actin-membrane protein network has a role in human sperm capacitation. Our results by Western blot indicate that ezrin is activated by phosphorylation of the threonine567 residue during capacitation. Co-immunoprecipitation studies revealed that, during sperm capacitation, the interaction between ezrin and RhoGDI1 increases, and phosphostaining of two dimensional electrophoresis gels showed that RhoGDI1 is phosphorylated, suggesting that RhoGDI1 dissociates from RhoA and leads to actin polymerization on the sperm head. We speculate that activated ezrin interacts with polymerized actin and the glycosylated membrane protein cd44 after capacitation. Blocking sperm capacitation using ezrin- or actin-specific monoclonal antibodies decreases their acrosome reaction (AR) rate, but has no effect on the AR alone. Taken together, our results show that a network consisting of ezrin, RhoGDI1, RhoA, F-actin and membrane proteins functions to influence the modifications that occur on the membrane of the sperm head during human sperm capacitation.
Wang
Lei
L
Laboratory of Reproductive Medicine, Department of Histology and Embryology, Nanjing Medical University, Nanjing 210029, China.
Chen
Wen
W
Zhao
Chun
C
Huo
Ran
R
Guo
Xue-Jiang
XJ
Lin
Min
M
Huang
Xiao-Yan
XY
Mao
Yun-Dong
YD
Zhou
Zuo-Min
ZM
Sha
Jia-Hao
JH
D000177:Acrosome / Q000378:metabolism; D020101:Acrosome Reaction; D000199:Actins / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D008297:Male; D008560:Membrane Fluidity; D008565:Membrane Proteins / Q000378:metabolism*; D011487:Protein Conformation; D013075:Sperm Capacitation; D013094:Spermatozoa / Q000737:chemistry / Q000378:metabolism*; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D000099149:Ezrin
D000199:Actins; D003598:Cytoskeletal Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D008565:Membrane Proteins; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D000099149:Ezrin; C569638:ARHGDIA protein, human