The sliding of the fibrous sheath through the axoneme proximally together with microtubule extrusion.

When activated mouse sperm were treated with Triton X-100 and dithiothreitol at pH 9.0, the plasma membrane and mitochondrial sheath of the sperm flagella were removed. These mitochondrion-free demembranated sperm flagella were perfused with Mg-ATP and trypsin to induce the sliding disintegration of microtubules from the axoneme. We observed that when the doublet microtubules associated with outer dense fibers extruded from the axoneme, the fibrous sheath (FS) was pulled proximally to the connecting piece from the annulus of the sperm flagellum accompanying the extrusion of microtubules. Furthermore, the FS sliding was cAMP-dependent and the maximal sliding velocity was about 3.7 +/- 0.1 microns/s in the presence of 1.0 mM ATP at 37 +/- 1 degrees C. Since the FS projected inward and attached opposite doublet microtubules 3 and 8 in the principal piece, our observation showed the possibility that doublet 3 and/or 8 participated in FS sliding.