Identification of an ADAM2-ADAM3 Complex on the Surface of Mouse Testicular Germ Cells and Cauda Epididymal Sperm

Hitoshi Nishimura,Diana G Myles,Paul Primakoff

doi:10.1074/jbc.m702268200

Hitoshi Nishimura, Diana G Myles + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m702268200

Copy DOI

Abstract

Male mice lacking ADAM2 (fertilin beta) or ADAM3 (cyritestin) are infertile; cauda epididymal sperm (mature sperm) from these mutant mice cannot bind to the egg zona pellucida. ADAM3 is barely present in Adam2-null sperm, despite normal levels of this protein in Adam2-null testicular germ cells (TGCs; sperm precursor cells). Here, we have explored the molecular basis for the loss of ADAM3 in Adam2-null TGCs to clarify the biosynthetic and functional linkage of ADAM2 and ADAM3. A small portion of total ADAM3 was found present on the surface of wild-type and Adam2(-/-) TGCs at similar levels. In the Adam2-null TGCs, however, surface-localized ADAM3 exhibited an increased amount of an endoglycosidase H-resistant form that may be related to instability of ADAM3. Moreover, we found a complex between ADAM2 and ADAM3 on the surface of TGCs and sperm. The intracellular chaperone calnexin was a component of the testicular ADAM2-ADAM3 complex. Our findings suggest that the association with ADAM2 is a key element for stability of ADAM3 in epididymal sperm. The presence of the ADAM2-ADAM3 complex in sperm also suggests a potential role of ADAM2 with ADAM3 in sperm binding to the egg zona pellucida.

Highlights

These findings suggest that ADAM3 plays a critical role(s) in sperm binding to the zona pellucida (ZP) and is delivered to the cell surface via a functional linkage with ADAM1a/ADAM2 (12, 18, 19)
Level of Surface ADAM3 in Adam2-null testicular germ cells (TGCs)—To examine why the level of ADAM3 is so low in Adam2-null sperm, we investigated when ADAM3 first appears on the cell surface
Whole cell lysates and cell-surface protein fractions prepared from wild-type, Adam2Ϫ/Ϫ, and Adam3Ϫ/Ϫ TGCs were analyzed by immunoblotting for several testicular proteins such as ADAM2, ADAM3, ADAM24, calmegin, calnexin, and PH-20 (Fig. 2)

Summary

Introduction

Sperm, corpus sperm, or cauda sperm (see Fig. 1). Many sperm plasma membrane proteins undergo post-translational modification, including proteolytic processing, and have multiple protein-protein interactions during membrane trafficking in the complicated process for differentiation and maturation of the sperm. These proteins have been known as endoplasmic digests (Fig. 4) revealed that ADAM2 was mostly sensitive to reticulum-resident molecular chaperones, but in recent work, Endo H in DIMs and DSMs of wild-type TGCs. Adam3-null cell-surface calnexin has been reported in a variety of cell types TGCs exhibited essentially the same digestion profiles of

Results

Conclusion