Cockroach GABAB receptor subtypes: molecular characterization, pharmacological properties and tissue distribution

Area of Science:

• Neuroscience
• Molecular Biology
• Entomology

Background:

• γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system (CNS).
• GABAB receptors, a class of G-protein-coupled receptors, modulate neuronal activity and are implicated in human neurological disorders.
• GABAB receptors in arthropods remain poorly understood.

Purpose of the Study:

• To clone and characterize GABAB receptor subtypes in the American cockroach, Periplaneta americana.
• To investigate the functional expression and pharmacological properties of these receptors.
• To determine the distribution of GABAB receptors within the American cockroach's nervous system and other tissues.

Main Methods:

• Cloning of complementary DNAs (cDNAs) for putative GABAB receptor subtypes 1 and 2 (PeaGB1 and PeaGB2).
• Co-expression of PeaGB1 and PeaGB2 in mammalian cells to study receptor activation and downstream signaling (cAMP production).
• Pharmacological profiling of the heteromeric receptor.
• Western blot analysis using polyclonal antibodies to detect receptor expression in the American cockroach CNS and other tissues.

Main Results:

• cDNAs for PeaGB1 and PeaGB2 were successfully cloned from P. americana.
• Co-expression of PeaGB1 and PeaGB2 in mammalian cells resulted in a GABA-activated, dose-dependent decrease in cAMP production.
• The pharmacological profile of PeaGB1/PeaGB2 heteromers differed from known mammalian and Drosophila GABAB receptors.
• PeaGB1 and PeaGB2 were detected in the CNS of the American cockroach.
• PeaGB1 exhibited broader expression, including salivary and male accessory glands, with evidence suggesting its role as an autoreceptor in specific neurons.

Conclusions:

• The study successfully identified and characterized GABAB receptor subtypes in the American cockroach, providing insights into their molecular and functional properties.
• The findings reveal a distinct pharmacological profile for insect GABAB receptors compared to their mammalian counterparts.
• The expression patterns suggest diverse roles for GABAB receptors in the American cockroach, including potential autoregulation in neuronal circuits and functions in reproductive tissues.