Mouse models for better understanding and treatment of Wilson Disease

Wilson disease (WD) is an autosomal recessive disorder caused by mutations in the copper transporter ATP7B that result in copper accumulation in tissues, broad spectrum of liver pathologies, and neurologic and psychiatric impairment. Without treatment, the disease is fatal. In our laboratory, we have extensively characterized the Atp7b-/- mice as model for WD. These studies led to the identification off nuclear receptors as early targets of elevated copper and demonstration that the agonist of nuclear receptor LXR helps to ameliorate WD in mouse model. We continue these studies and also develop additional cell-specific Atp7b knockouts to better understand the role of copper in disease development.

 Relevant publications:

• Hepatic Steatosis in the Mouse Model of Wilson Disease Coincides with a Muted Inflammatory Response. Gottlieb A, Dev S, DeVine L, Gabrielson KL, Cole RN, Hamilton JP, Lutsenko S.

• Systemic deletion of Atp7b modifies the hepatocytes' response to copper overload in the mouse models of Wilson disease. Muchenditsi A, Talbot CC Jr, Gottlieb A, Yang H, Kang B, Boronina T, Cole R, Wang L, Dev S, Hamilton JP, Lutsenko S.

The regulatory role of copper in the intestine

We found that copper levels in intestine are tightly regulated and control processing of dietary fat. Either high or low copper is detrimental to the proper processing of chylomicrons, lipoprotein particles that mediate dietary fat absorption. By using mouse models and 3-dimensional primary organoids (see image generated by Hannah Pierson), we aim to understand how copper regulate nutrient absorption at the molecular and cellular level.

 Relevant publications:

• Obesity is associated with copper elevation in serum and tissues. Yang H, Liu CN, Wolf RM, Ralle M, Dev S, Pierson H, Askin F, Steele KE, Magnuson TH, Schweitzer MA, Wong GW, Lutsenko S.Metallomics. 2019 Aug 1;11(8):1363-1371.

• Copper Transport and Disease: What Can We Learn from Organoids? Pierson H, Yang H, Lutsenko S.Annu Rev Nutr. 2019 Aug 21;39:75-94.

Copper homeostasis in brain development

Copper is essential for brain development and function. It is especially enriched in some regions, such as choroid plexus, sub-ventricle region, and locus coeruleus (see image). Copper transporter ATP7B is expressed in the brain in cell-specific and time-specific manner. Loss of ATP7B is associated with copper accumulation in the brain, abnormal lipid content, catecholamine misbalance, and morphological changes. In humans, these consequences of ATP7B inactivation are associated with neurologic and psychiatric abnormalities, known as Wilson disease. Current projects in the lab aim to better understand the role of ATP7B in noradrenergic neurons, elucidate contribution of ATP7B to oligodendrocyte development and neuronal myelination, and uncover mechanism underlying Wilson disease pathogenesis.

 Relevant publications:

• Copper and the brain noradrenergic system. Lutsenko S, Washington-Hughes C, Ralle M, Schmidt K.J Biol Inorg Chem. 2019 Dec;24(8):1179-1188.

• Localization of the Locus Coeruleus in the Mouse Brain. Schmidt K, Bari B, Ralle M, Washington-Hughes C, Muchenditsi A, Maxey E, Lutsenko S.

• ATP7A and ATP7B copper transporters have distinct functions in the regulation of neuronal dopamine-β-hydroxylase. Schmidt K, Ralle M, Schaffer T, Jayakanthan S, Bari B, Muchenditsi A, Lutsenko S.

New regulators of copper homeostasis

Our collaborative studies using genome-wide siRNA screen identified several proteins with previously unknown roles in copper homeostasis.  We are particularly interested in the RNA-transporting protein hnRNPA2B1, which has a well know function in trafficking of mRNA for a myelin basic protein in oligodendrocytes.  The loss of hnRNPA2/B1 lowers cellular copper content, whereas high copper upregulates specific isoforms of this protein. We are now investigating the mechanisms behind these phenomena.  We also found that the ankyrin domain protein ANKRD9 plays an important role in copper balance and regulate abundance and assembly of IMPDH2, the rate limiting enzyme in couples GTP biosynthesis.  We are now investigating how ANKRD9 couples copper homeostasis and GTP metabolism. 

 Relevant publication:

• ANKRD9 is a metabolically-controlled regulator of IMPDH2 abundance and macro-assembly. Hayward D, Kouznetsova VL, Pierson HE, Hasan NM, Guzman ER, Tsigelny IF, Lutsenko S.J Biol Chem. 2019 Sep 27;294(39):14454-14466.

Mechanisms of copper transport and distribution

Copper (Cu) is utilized by important metabolic enzymes in different cellular compartments (mitochondria, cytosol, secretory pathway) and cells developed sophisticated mechanisms to control Cu delivery to the appropriate targets in a timely fashion.  The central role in the Cu distribution pathways belongs to the small cytosolic Cu shuttles (Cu chaperones) and Cu transporters.  In our lab, we are interested in how Cu chaperones and transporters work together and how Cu is transported.  These structure-function function studies utilize adenovirus-mediated protein expression, functional assay, and, recently, work towards structural analysis of these proteins using Cryo-EM.

Relevant publications:

• Analysis of Wilson disease mutations revealed that interactions between different ATP7B mutants modify their properties. Roy S, McCann CJ, Ralle M, Ray K, Ray J, Lutsenko S, Jayakanthan S.Sci Rep. 2020 Aug 10;10(1):13487. doi: 10.1038/s41598-020-70366-7.

• Single nucleotide polymorphisms in the human ATP7B gene modify the properties of the ATP7B protein. McCann CJ, Jayakanthan S, Siotto M, Yang N, Osipova M, Squitti R, Lutsenko S.Metallomics. 2019 Jun 19;11(6):1128-1139. doi: 10.1039/c9mt00057g.

• Human copper transporter ATP7B (Wilson disease protein) forms stable dimers in vitro and in cells. Jayakanthan S, Braiterman LT, Hasan NM, Unger VM, Lutsenko S.J Biol Chem. 2017 Nov 17;292(46):18760-18774.