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Characterization of CD46 and β 1 integrin dynamics during sperm acrosome reaction

View Article: PubMed Central - PubMed

ABSTRACT

The acrosome reaction (AR) is a process of membrane fusion and lytic enzyme release, which enables sperm to penetrate the egg surroundings. It is widely recognized that specific sperm proteins form an active network prior to fertilization, and their dynamic relocation is crucial for the sperm-egg fusion. The unique presence of the membrane cofactor protein CD46 in the sperm acrosomal membrane was shown, however, its behaviour and connection with other sperm proteins has not been explored further. Using super resolution microscopy, we demonstrated a dynamic CD46 reorganisation over the sperm head during the AR, and its interaction with transmembrane protein integrins, which was confirmed by proximity ligation assay. Furthermore, we propose their joint involvement in actin network rearrangement. Moreover, CD46 and β1 integrins with subunit α3, but not α6, are localized into the apical acrosome and are expected to be involved in signal transduction pathways directing the acrosome stability and essential protein network rearrangements prior to gamete fusion.

No MeSH data available.


Dynamics of CD46, β1 integrin and actin captured by STED super-resolution microscopy.(line I and III) Actin (red) fills the apical acrosome and equatorial segment of an intact sperm head, it copies the plasma membrane and overlays the CD46 (green, line I) labelled acrosome in a thin line pattern (see red arrow). (line III) β1 integrin and actin display a similar localization in the apical acrosome cap region (plasma and acrosomal membrane). The perforatorium is filled with actin, but clearly marked with the β1 integrin. (line II and IV) Actin (red) is confined to the equatorial and postacrosomal segment in the acrosome reacted sperm. CD46 (green, line II) and β1 (green, line IV) relocation progress during the AR is visible. DAPI (blue); Scale bar represents 1 μm.
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f6: Dynamics of CD46, β1 integrin and actin captured by STED super-resolution microscopy.(line I and III) Actin (red) fills the apical acrosome and equatorial segment of an intact sperm head, it copies the plasma membrane and overlays the CD46 (green, line I) labelled acrosome in a thin line pattern (see red arrow). (line III) β1 integrin and actin display a similar localization in the apical acrosome cap region (plasma and acrosomal membrane). The perforatorium is filled with actin, but clearly marked with the β1 integrin. (line II and IV) Actin (red) is confined to the equatorial and postacrosomal segment in the acrosome reacted sperm. CD46 (green, line II) and β1 (green, line IV) relocation progress during the AR is visible. DAPI (blue); Scale bar represents 1 μm.

Mentions: A detailed mutual localization of CD46 and β1 integrins was visualised on freshly released epididymal sperm with an intact acrosome (Fig. 5AI, S2 video image). In this case, the presence of CD46 was detected solely in the acrosomal cap in both the outer and inner acrosomal membranes, but not on the plasma membrane covering the acrosome region. Contrary to that, the β1 integrin subunit was present in the plasma membrane where it was detected in the area of acrosome cap (AC) and the hook marking the shape of the apical and dorsal sperm head (Fig. 5AI; 5BI and Fig. 6III, see the arrows). Unlike CD46, β1 integrins are present in an intact sperm head only in the outer acrosomal membrane, but not in the inner one (Fig. 5AI) and only later during the AR is the protein relocated over the inner acrosome membrane, equatorial segment and eventually the whole sperm head.


Characterization of CD46 and β 1 integrin dynamics during sperm acrosome reaction
Dynamics of CD46, β1 integrin and actin captured by STED super-resolution microscopy.(line I and III) Actin (red) fills the apical acrosome and equatorial segment of an intact sperm head, it copies the plasma membrane and overlays the CD46 (green, line I) labelled acrosome in a thin line pattern (see red arrow). (line III) β1 integrin and actin display a similar localization in the apical acrosome cap region (plasma and acrosomal membrane). The perforatorium is filled with actin, but clearly marked with the β1 integrin. (line II and IV) Actin (red) is confined to the equatorial and postacrosomal segment in the acrosome reacted sperm. CD46 (green, line II) and β1 (green, line IV) relocation progress during the AR is visible. DAPI (blue); Scale bar represents 1 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036054&req=5

f6: Dynamics of CD46, β1 integrin and actin captured by STED super-resolution microscopy.(line I and III) Actin (red) fills the apical acrosome and equatorial segment of an intact sperm head, it copies the plasma membrane and overlays the CD46 (green, line I) labelled acrosome in a thin line pattern (see red arrow). (line III) β1 integrin and actin display a similar localization in the apical acrosome cap region (plasma and acrosomal membrane). The perforatorium is filled with actin, but clearly marked with the β1 integrin. (line II and IV) Actin (red) is confined to the equatorial and postacrosomal segment in the acrosome reacted sperm. CD46 (green, line II) and β1 (green, line IV) relocation progress during the AR is visible. DAPI (blue); Scale bar represents 1 μm.
Mentions: A detailed mutual localization of CD46 and β1 integrins was visualised on freshly released epididymal sperm with an intact acrosome (Fig. 5AI, S2 video image). In this case, the presence of CD46 was detected solely in the acrosomal cap in both the outer and inner acrosomal membranes, but not on the plasma membrane covering the acrosome region. Contrary to that, the β1 integrin subunit was present in the plasma membrane where it was detected in the area of acrosome cap (AC) and the hook marking the shape of the apical and dorsal sperm head (Fig. 5AI; 5BI and Fig. 6III, see the arrows). Unlike CD46, β1 integrins are present in an intact sperm head only in the outer acrosomal membrane, but not in the inner one (Fig. 5AI) and only later during the AR is the protein relocated over the inner acrosome membrane, equatorial segment and eventually the whole sperm head.

View Article: PubMed Central - PubMed

ABSTRACT

The acrosome reaction (AR) is a process of membrane fusion and lytic enzyme release, which enables sperm to penetrate the egg surroundings. It is widely recognized that specific sperm proteins form an active network prior to fertilization, and their dynamic relocation is crucial for the sperm-egg fusion. The unique presence of the membrane cofactor protein CD46 in the sperm acrosomal membrane was shown, however, its behaviour and connection with other sperm proteins has not been explored further. Using super resolution microscopy, we demonstrated a dynamic CD46 reorganisation over the sperm head during the AR, and its interaction with transmembrane protein integrins, which was confirmed by proximity ligation assay. Furthermore, we propose their joint involvement in actin network rearrangement. Moreover, CD46 and β1 integrins with subunit α3, but not α6, are localized into the apical acrosome and are expected to be involved in signal transduction pathways directing the acrosome stability and essential protein network rearrangements prior to gamete fusion.

No MeSH data available.