Localization and identification of sumoylated proteins in human sperm: excessive sumoylation is a marker of defective spermatozoa.
BACKGROUND
Sumoylation is a type of post-translational modification that is implicated in the regulation of numerous cellular events. However, its role in the function of human sperm has not yet been characterized.


RESULTS
In this study, both immunofluorescence and electron microscopy revealed that small ubiquitin-like modifiers (SUMO) SUMO1 and SUMO2/3 were highly enriched in the neck area of human sperm that is associated with the redundant nuclear envelope and were also detectable in the flagella and some head regions. Similar localization patterns of SUMO were also observed in mouse and fly sperm. Nonmotile, two-tailed, curled tailed, misshapen, microcephalic (small head) and aciphalic (no head) sperm exhibited abnormally high levels of sumoylation in their neck and tail regions relative to normal sperm. Numerous sumoylated proteins, ranging from 20 to 260 kDa, were detected via western blotting and identified by mass spectrometry, and 55 SUMO targets that were present specifically in human sperm, and not in the control fraction, corresponded to flagella proteins, proteins involved in the maturation and differentiation of sperm, heat shock proteins and important glycolytic and mitochondrial enzymes. The targets that were identified included proteins with specific functions in germ cells and sperm, such as heat shock-related 70-kDa protein 2, outer dense fiber protein 3, A-kinase anchor proteins 3 and 4, L-lactate dehydrogenase C, sperm protein associated with the nucleus on the X chromosome B/F, valosin-containing protein, seminogelins, histone H4 and ubiquitin. Coimmunoprecipitation experiments confirmed the sumoylation of semenogelin and indicated that some sperm proteins are modified by sumoylation and ubiquitination simultaneously.


CONCLUSIONS
Numerous proteins are modified by sumoylation in human sperm; excessive sumoylation is a marker of defective spermatozoa.
Department of Biology, Stern College, Yeshiva University, 245 Lexington Avenue, New York, NY 10016, USA. vigodner@yu.edu
Margarita
M
Vigodner
Vibha
V
Shrivastava
Leah Elisheva
LE
Gutstein
Jordana
J
Schneider
Edward
E
Nieves
Marc
M
Goldstein
Miriam
M
Feliciano
Myrasol
M
Callaway
D000818:Animals; D015415:Biomarkers / Q000737:chemistry / Q000378:metabolism; D048430:Cell Shape; D004175:Diptera; D004822:Epididymis / Q000166:cytology; D006801:Humans; D007248:Infertility, Male / Q000378:metabolism* / Q000473:pathology; D019476:Insect Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008970:Molecular Weight; D009685:Nuclear Envelope / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D025842:SUMO-1 Protein / Q000737:chemistry / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000737:chemistry / Q000378:metabolism*; D013045:Species Specificity; D013094:Spermatozoa / Q000002:abnormalities / Q000378:metabolism* / Q000648:ultrastructure; D058207:Sumoylation; D054875:Ubiquitination; D014452:Ubiquitins / Q000737:chemistry / Q000378:metabolism*
D015415:Biomarkers; D019476:Insect Proteins; D010446:Peptide Fragments; D011506:Proteins; D025842:SUMO-1 Protein; C117909:SUMO2 protein, human; C492189:SUMO3 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; D014452:Ubiquitins