mTORC1/rpS6 signaling complex modifies BTB transport function: an in vivo study using the adjudin model

Area of Science:

• Reproductive Biology
• Molecular Endocrinology
• Cell Signaling

Background:

• The mTORC1/rpS6 pathway regulates the Sertoli cell blood-testis barrier (BTB).
• Inhibition of mTORC1 tightens the BTB, while activation by rpS6 overexpression loosens it.
• rpS6 phosphorylation increases during BTB remodeling in specific testicular stages.

Purpose of the Study:

• To investigate the role of a constitutively active rpS6 mutant (p-rpS6-MT) in BTB dynamics in vivo.
• To assess the potential of p-rpS6-MT to enhance male contraceptive delivery and efficacy.
• To characterize the BTB transport function in relation to rpS6 signaling.

Main Methods:

• Overexpression of a quadruple phosphomimetic rpS6 mutant (p-rpS6-MT) in rat testes using in vivo jet-PEI transfection.
• Utilizing site-directed mutagenesis to create the p-rpS6-MT construct (S235E/S236E/S240E/S244E).
• Administering the nonhormonal male contraceptive adjudin in combination with p-rpS6-MT overexpression.

Main Results:

• Overexpression of p-rpS6-MT induced BTB remodeling, leading to a 'leaky' barrier.
• This facilitated the entry of adjudin into the adluminal compartment.
• Combined treatment potentiated adjudin's bioavailability by modifying the BTB, enabling lower drug doses.

Conclusions:

• Constitutively active rpS6 signaling can effectively remodel the BTB in vivo.
• Modifying the BTB via p-rpS6-MT enhances the delivery and efficacy of male contraceptives like adjudin.
• This strategy offers a potential approach to reduce drug toxicity and improve male contraceptive development.