Stabilization of membrane-associated alpha-L-fucosidase by the human sperm equatorial segment.
Previous reports from this laboratory documented the existence of two novel isoforms of alpha-L-fucosidase in human semen and showed that membrane-associated alpha-L-fucosidase is cryptically held within the acrosomal compartment and enriched within the sperm equatorial segment. The occurrence of these novel isoforms is provocative. Sperm proteins potentially involved in sperm-egg interactions must maintain their functional integrity as they travel through the female reproductive tract. The goal of this project was to investigate the stability of membrane-associated alpha-L-fucosidase in human sperm. Whole seminal plasma and Percoll purified sperm cell populations were incubated for 72 h at 37 degrees C, with 5% CO(2) or ambient air. At various times during prolonged incubation, sperm cells were permeabilized with 0.1% Triton X-100 and enzyme assays using the fluorogenic substrate 4-MU-fuc were performed to evaluate the stability of both the seminal plasma and membrane-associated alpha-L-fucosidase. Here, we report seminal plasma alpha-L-fucosidase activity rapidly decreased within 24 h. Conversely, alpha-L-fucosidase activity from Percoll purified sperm cell populations persisted up to 72 h. Data from these experiments support the notions that (i) membrane-associated alpha-L-fucosidase is stable for extended periods of time, consistent with a possible role in sperm-egg interaction and (ii) membrane domains and compartmentalization within the human sperm are key to preserving protein integrity.
Venditti
Jennifer J
JJ
Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA. jjv2@lehigh.edu
Bean
Barry S
BS
D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D013094:Spermatozoa / Q000201:enzymology*; D005644:alpha-L-Fucosidase / Q000378:metabolism*
D008565:Membrane Proteins; D005644:alpha-L-Fucosidase