Indiana University-Purdue University Indianapolis (IUPUI) / Glioblastoma is the most aggressive type of brain cancer with very poor prognosis. Due to the lack of understanding of underlying mechanisms, there are no anti-invasive clinical therapeutics available. SRC terminal kinase (SRC) is a tumorigenic protein that is highly expressed in glioblastoma samples. SRC inhibitor kinase 1 (SRCIN1), also known as p140Cap is a negative regulator of SRC. Silencing SRCIN1 results in increased tumor invasion. Our lab has discovered two novel scaffolding proteins Spinophilin (Spn) and neurabin (Nrb) that bind to SRCIN1. They may play a role in regulating SRCIN1 activity, as well as its downstream effects that ultimately decrease SRC’s tumorigenic activity. Spn and Nrb are two scaffolding proteins that are heavily expressed in the central nervous system. Spn knockout mice develop more tumors, indicating that Spn acts as a tumor suppressor protein, although the mechanisms of Spn’s anti-tumor properties are not well understood. Spn and Nrb are PP1 targeting proteins that target PP1 to other substrates, resulting in dephosphorylation and alteration of function. We found that PP1 increases Spn association with SRCIN1, but decreases Nrb association with SRCIN1, indicating that the two proteins might have opposite effects to balance the activity of p140Cap. We also found that cyclin-dependent kinase 5 (CDK5) phosphorylates and regulates the association of these scaffolding proteins with the tumor suppressor protein, p140Cap. Understanding these mechanisms provides insight into new therapeutic targets that may ultimately decrease SRC activity and its tumorigenic and invasive properties.

Indiana University-Purdue University Indianapolis (IUPUI) / The striatum is a key brain region involved in regulating motor output and integration. The dorsal and ventral subdivisions of the striatum work in concert to mediate the reinforcing and motor behavioral outputs of the striatum. Moreover, dysfunction of these striatal regions is involved in various diseases including Parkinson’s disease and drug addiction. Therefore, understanding and characterizing biochemical and molecular changes within the striatum associated with these diseases is key in devolving novel therapeutics to treat these disease states. The main output neurons of the striatum are GABAergic, medium-spiny neurons (MSNs), and striatal functionality is mediated by neuroplastic changes in MSN activity. Within MSNs, dopaminergic receptor activation triggers a cascade of reversable phosphorylation, which is facilitated by the activation of specific protein kinases and inhibition of specific protein phosphatases. In comparison to the 350 serine/threonine protein kinases expressed within the striatum, there are only 40 major serine/threonine protein phosphatases. However, serine/threonine protein phosphatases, such as protein phosphatase 1 (PP1), gain their target specificity by interacting with phosphatase-targeting proteins. Within the striatum, the neurabins, termed neurabin and spinophilin, are the most abundant PP1 targeting proteins in dendritic spines. Spinophilin’s expression in the striatum has been strongly characterized, and spinophilin has been shown to regulate striatal-dependent motor-skill learning and amphetamine-induced locomotor sensitization. In contrast to spinophilin, neurabin’s expression within the striatum and its involvement in these striatal-dependent behaviors has not been fully probed. I found that neurabin expression in the striatum is not sex-dependent but is age-dependent. In addition to these data, I also present validation of new global, constitutive and conditional neurabin knock-out mouse lines. Finally, I present data that, unlike previous studies in spinophilin knockout mice, neurabin knockout mice have enhanced striatal-dependent motor-skill learning, but do not impact amphetamine-induced locomotor sensitization. Further characterization of neurabin’s expression in the striatum, and its role in these key striatal behaviors could provide a druggable target for therapeutics designed to address striatal dysfunction.

Neurabin, a cytoskeletal protein, has been shown to be required for normal dopamine signalling, and dopaminergic systems have been previously implicated in the pathophysiology of anxiety disorders, including generalized social anxiety disorder. And results from neuroimaging studies have implicated the anterior cingulate cortex (ACC) in depression and anxiety disorders. However, lesion studies have failed to produce the expected deficits. Here, we demonstrate that the injections of muscimol and midazolam into the ACC reduced anxiety- and depression-like behaviours, and that complete absence of neurabin reduced anxiety-like behaviour but increased depression-like behaviour. However, reduction of neurabin by injecting neurabin-targeted siRNA into the ACC reduced anxiety-like behaviour but did not affect depression-like behaviour. This study provides evidence that the imbalance of excitatory and inhibitory activity in the ACC alters affective disorders, and that neurabin may be critical for the modulation of these behaviours.

Neurabin, a cytoskeletal protein, has been shown to be required for normal dopamine signalling, and dopaminergic systems have been previously implicated in the pathophysiology of anxiety disorders, including generalized social anxiety disorder. And results from neuroimaging studies have implicated the anterior cingulate cortex (ACC) in depression and anxiety disorders. However, lesion studies have failed to produce the expected deficits. Here, we demonstrate that the injections of muscimol and midazolam into the ACC reduced anxiety- and depression-like behaviours, and that complete absence of neurabin reduced anxiety-like behaviour but increased depression-like behaviour. However, reduction of neurabin by injecting neurabin-targeted siRNA into the ACC reduced anxiety-like behaviour but did not affect depression-like behaviour. This study provides evidence that the imbalance of excitatory and inhibitory activity in the ACC alters affective disorders, and that neurabin may be critical for the modulation of these behaviours.

<p> The striatum is a key brain region involved in regulating motor output and integration. The dorsal and ventral subdivisions of the striatum work in concert to mediate the reinforcing and motor behavioral outputs of the striatum. Moreover, dysfunction of these striatal regions is involved in various diseases including Parkinson’s disease and drug addiction. Therefore, understanding and characterizing biochemical and molecular changes within the striatum associated with these diseases is key in devolving novel therapeutics to treat these disease states. The main output neurons of the striatum are GABAergic, medium-spiny neurons (MSNs), and striatal functionality is mediated by neuroplastic changes in MSN activity. Within MSNs, dopaminergic receptor activation triggers a cascade of reversable phosphorylation, which is facilitated by the activation of specific protein kinases and inhibition of specific protein phosphatases. In comparison to the 350 serine/threonine protein kinases expressed within the striatum, there are only 40 major serine/threonine protein phosphatases. However, serine/threonine protein phosphatases, such as protein phosphatase 1 (PP1), gain their target specificity by interacting with phosphatase-targeting proteins. Within the striatum, the neurabins, termed neurabin and spinophilin, are the most abundant PP1 targeting proteins in dendritic spines. Spinophilin’s expression in the striatum has been strongly characterized, and spinophilin has been shown to regulate striatal-dependent motor-skill learning and amphetamine-induced locomotor sensitization. In contrast to spinophilin, neurabin’s expression within the striatum and its involvement in these striatal-dependent behaviors has not been fully probed. I found that neurabin expression in the striatum is not sex-dependent but is age-dependent. In addition to these data, I also present validation of new global, constitutive and conditional neurabin knock-out mouse lines. Finally, I present data that, unlike previous studies in spinophilin knockout mice, neurabin knockout mice have enhanced striatal-dependent motor-skill learning, but do not impact amphetamine-induced locomotor sensitization. Further characterization of neurabin’s expression in the striatum, and its role in these key striatal behaviors could provide a druggable target for therapeutics designed to address striatal dysfunction.   </p>