Heroin use disorder (HUD) represents an enduring public health issue resulting in significant socioeconomic
burdens to the United States, with domestic opiate-related deaths quadrupling from 1999 to 2017. Despite this
the neurobiological mechanisms underlying HUD remain poorly understood. All drugs of abuse modulate
dopaminergic signaling and have long been thought of as disorders of dopamine (DA) signaling. However,
pharmacotherapeutic interventions targeting receptor mediated DA-signaling have not resulted in efficacious
treatments. Our laboratory recently identified a novel signaling moiety for DA, termed dopaminylation, whereby
DA itself acts as a post-translational modification (PTM) on substrate proteins via transamidation by the
Transglutaminase 2 (TGM2) enzyme. I sought, then, to unbiasedly identify additional synaptic substrates of
dopaminylation in vivo, utilizing a novel chemical tagging approach coupled to mass spectrometry. I identified
164 novel putative synaptic substrates of dopaminylation in Nucleus Accumbens (NAc), both in the context of
normal neural function and in response to abstinence from chronic heroin self-administration. Following
validation of a number of putative substrates, I turned my focus to gCaMKII as: 1) it is highly abundant 2) it is
dopaminylated at a single amino acid residue, located within it’s autoinhibitory helix (glutamine [Q]285), a site
that exists only two amino acids away from the critical threonine (T) residue 287. T287 is phosphorylated to direct
Calmodulin (CaM) sequestration and subsequent nuclear translocation – thus, this site, represents an exciting
‘test’ case for establishing the importance of this signaling moiety in post synaptic plasticity 3) it is upregulated
in its dopaminylation state following abstinence from heroin SA, an effect that persists to AD14 and 4)represents
a critical substrate involved in mediating long range signals from the synapse to the nucleus in brain, ultimately
promoting CREB activation. gCaMKII is a synaptic protein demonstrated to be necessary for learning/memory,
late-long-term-potentiation (LTP) and excitation transcription coupling. CREB is an important transcription factor
in brain implicated in all types of SUD, where dynamic alterations in activation have been observed to affect
drug-related behaviors. I have additionally demonstrated that monoamine molecules can infiltrate striatal and
cortical neurons in vitro, as well as that treatment of these neurons with DA induces gCaMKII dopaminylation. I
also observed the dynamic regulation of gCaMKII/CaM localization and subsequent downstream CREB signaling
in response to DA treatment in primary cortical-striatal neuronal culture. I therefore hypothesize that
gCaMKIIQ285dop may represent a novel dopaminergic signaling moiety in brain, and may play a direct role in
mediating heroin relapse behaviors via aberrant modulation of CREB signaling in NAc.