The guinea pig sperm plasma membrane protein, PH-20, reaches the surface via two transport pathways and becomes localized to a domain after an initial uniform distribution.
The PH-20 protein is first detected in the Golgi complex at the start of differentiation of round spermatids into a polarized cell (spermiogenesis), and next appears in the membrane of the developing secretory granule (the acrosome). Thereafter, a second population of PH-20 is inserted directly into the plasma membrane. Initially, both the acrosomal membrane (PH-20AM) and the plasma membrane (PH-20PM) populations are uniformly distributed in each membrane. Subsequently, PH-20AM is restricted to the inner acrosomal membrane, and during epididymal passage PH-20PM becomes localized to the posterior head surface domain. Therefore, the PH-20 protein does not become localized to either domain by intracellular sorting and insertion into a localized domain, but by restriction following uniform insertion. When the sperm undergoes Ca2+-regulated exocytosis (the acrosome reaction), the inner acrosomal membrane becomes confluent with the plasma membrane. Consequently, the population of PH-20AM is now inserted into the plasma membrane. The PH-20 protein isolated from developing testicular cells contains a major form, approximately 66 kDa, and a minor form, approximately equal to 56 kDa, but it remains to be determined if each form enters only one or both pathways. The developmental control of surface expression of PH-20 during spermiogenesis in the guinea pig may reflect the regulation of a protein involved in sperm-egg adhesion. (Primakoff, P., Hyatt, H., and Myles, D. g. (1985), J. Cell. Biol. 101, 2239-2244).
Phelps
B M
BM
Myles
D G
DG
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006056:Golgi Apparatus / Q000648:ultrastructure; D006168:Guinea Pigs; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D013091:Spermatogenesis; D013094:Spermatozoa / Q000166:cytology*
D008565:Membrane Proteins