CELLULAR REQUIREMENTS FOR MBLAC1 EXPRESSION AS ASSESSED IN MBLAC1-/- MOUSE EMBRYONIC FIBROBLASTS

The majority of research on drug addiction centers on dopamine (DA)- driven synaptic plasticities and how these changes ultimately lead to compulsive drug seeking. However, growing evidence supports a role of glial factors in various steps that lead to drug abuse and addiction. In this regard, significant evidence implicates glial glutamate (Glu) transporters (GLT-1) and cystine/Glu exchangers (xCT) in determining synaptic and extrasynaptic levels of Glu that support the acute and chronic actions of drugs of abuse. -lactam antibiotics have been found in rodent models to upregulate CNS GLT-1 and xCT and thereby contribute to reinstatement after chronic drug exposure and withdrawal.
Previously, the Blakely lab identified a glial expressing gene, swip-10, in Caenorhabditis elegans, whose deletion results in the hyperdominergic phenotype Swimming-Induced Paralysis (Swip), supported by Glu signalingdependent DA neuron hyperexcitability that ultimately drives oxidative stress and DA neuron degeneration. Both SWIP-10 and its putative mammalian ortholog MBLAC1 possess a highly conserved metallo -lactamase domain, and MBLAC1 has been found to bind the Glu modulating, b-lactam antibiotic ceftriaxone (Cef). Indeed, immunodepletion studies indicate that MBLAC1 may be the major highaffinity Cef-binding protein in the brain, leading to the hypothesis that MBLAC1 has a Glu modulatory role(s). Recently a functional role of MBLAC1 been proposed, involving activity as a 3’ exonuclease that processes polyA- mRNAs, including RNAs encoding cell replication-dependent histones. How this role, or others, may support the actions of MBLAC1 in the brain and the non-microbial actions of Cef to extracellular Glu homeostasis, is unclear. Recently, the Blakely lab generated Mblac1-/- mice as a tool to investigate these issues. The following work investigated the requirements of MBLAC1 in growth and the actions of Cef in mouse embryonic fibroblasts (MEFs) cultured from either Mblac1+/+ and Mblac1-/- mice. The presented data suggested that Mblac1-/- MEFs display attenuated growth and cell proliferation relative to Mblac1+/+ MEFs. For the first time, the in vitro protective actions of Cef against oxidative stress is shown to be dependent on MBLAC1. The following studies presented contribute to a definition of the role of MBLAC1 and as a Cef binding protein in native preparations, with findings that can drive models for the role of MBLAC1 in the CNS.