Defects in secretory pathway trafficking during sperm development in Adam2 knockout mice

Area of Science:

• Reproductive biology
• Spermatogenesis
• Protein trafficking

Background:

• ADAM (a disintegrin and metalloproteinase) proteins are crucial for sperm function.
• Previous studies indicated post-translational loss of ADAM proteins in null mice, but mechanisms remained unclear.

Purpose of the Study:

• To investigate the timing and mechanisms of ADAM2 and ADAM3 protein loss in Adam2-null and Adam3-null mice.
• To elucidate the role of protein trafficking in ADAM protein regulation during sperm maturation.

Main Methods:

• Analysis of ADAM2 and ADAM3 protein levels in testicular and epididymal sperm from Adam2-null and Adam3-null mice.
• Biochemical assays including Endoglycosidase H resistance and Triton X-100 solubility.
• Cellular localization studies of ADAM proteins.

Main Results:

• ADAM2 is lost during spermatogenesis in Adam3-null mice.
• In Adam2-null mice, most ADAM3 is lost during spermatogenesis, with the remainder lost during epididymal transit.
• ADAM3 in Adam2-null mice reaches the Golgi but fails to traffic to the cell surface, suggesting a trafficking defect.
• ADAM2 and ADAM3 are found in a Triton X-100 insoluble fraction in testicular sperm, potentially indicating a sorting platform.

Conclusions:

• ADAM protein loss in null mice occurs at specific stages of sperm development and epididymal transit.
• Disrupted protein trafficking, particularly for ADAM3 in Adam2-null mice, contributes to protein loss.
• The Triton X-100 insoluble compartment may play a role in ADAM protein sorting and cell surface localization.