Acidic hyaluronidase activity is present in mouse sperm and is reduced in the absence of SPAM1: evidence for a role for hyaluronidase 3 in mouse and human sperm.
The molecular mechanisms underlying sperm penetration of the physical barriers surrounding the oocyte have not been completely delineated. Although neutral-active or "reproductive" hyaluronidases (hyases), exemplified by Sperm Adhesion Molecule 1 (SPAM1), are thought to be responsible for hyaluronan digestion in the egg vestments and for sperm-zona binding, their roles in mouse sperm have been recently questioned. Here we report that acidic "somatic" Hyaluronidase 3 (HYAL3), a homolog of SPAM1 with 74.6% structural similarity, exists in two isoforms in human ( approximately 47 and approximately 55 kDa) and mouse ( approximately 44 and approximately 47 kDa) sperm, where it resides on the plasma membrane over the head and midpiece. Mouse isoforms are differentially distributed in the soluble (SAP), membrane (MBP), and acrosome-reacted (AR) fraction where they are most abundant. Comparisons of zymography of Hyal3 null and wild-type (WT) AR and MBP fractions show significant HYAL3 activity at pH 3 and 4, and less at pH 7. At pH 4, a second acid-active hyase band at approximately 57 kDa is present in the AR fraction. HYAL3 activity was confirmed using immunoprecipitated HYAL3 and spectrophotometry. In total proteins, hyase activity was higher at pH 6 than at 4, where Spam1 nulls had significantly (P < 0.01) diminished activity implicating an acidic optima for murine SPAM1. Although fully fertile, Hyal3 null sperm showed delayed cumulus penetration and reduced acrosomal exocytosis. HYAL3 is expressed in epididymal tissue/fluid, from where it is acquired by caudal mouse sperm in vitro. Our results reveal concerted activity of both neutral- and acid-active hyaluronidases in sperm.
Reese
Kristen L
KL
Department of Biological Sciences, University of Delaware, Newark, Delaware 19716, USA.
Aravindan
Rolands G
RG
Griffiths
Genevieve S
GS
Shao
Minghai
M
Wang
Yipei
Y
Galileo
Deni S
DS
Atmuri
Vasantha
V
Triggs-Raine
Barbara L
BL
Martin-Deleon
Patricia A
PA
D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism* / Q000502:physiology; D004822:Epididymis / Q000201:enzymology / Q000502:physiology; D006801:Humans; D006821:Hyaluronoglucosaminidase / Q000378:metabolism* / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D013084:Sperm-Ovum Interactions / Q000502:physiology; D013094:Spermatozoa / Q000201:enzymology* / Q000502:physiology
D015815:Cell Adhesion Molecules; D006821:Hyaluronoglucosaminidase; C066852:hyaluronidase PH-20