Interaction of the Brain-Selective Sulfotransferase SULT4A1 with Other Cytosolic Sulfotransferases: Effects on Protein Expression and Function

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Abstract
SULT4A1 is a brain-selective sulfotransferase-like protein that has recently been shown to be essential for normal neuronal development in mice. In the present study, SULT4A1 was found to co-localize with SULT1A1/3 in human brain neurons. Using immunoprecipitation, SULT4A1 was shown to interact with both SULT1A1 and 1A3 when expressed in human cells. Mutation of the conserved dimerization motif located in the C-terminus of the sulfotransferases prevented this interaction. Both ectopically expressed and endogenous SULT4A1 decreased SULT1A1/3 protein levels in neuronal cells, which was also prevented by mutation of the dimerization motif. During differentiation of neuronal SH-SY5Y cells, there was a loss in SULT1A1/3 protein but an increase in SULT4A1 protein. This resulted in an increase in the toxicity of dopamine, a substrate for SULT1A3. Inhibition of SULT4A1 using siRNA abrogated the loss in SULT1A1/3 and reversed dopamine toxicity. These results show a reciprocal relationship between SULT4A1 and the other sulfotransferases suggesting that it may act as a chaperone to control the expression of SULT1A1/3 in neuronal cells. SIGNIFICANCE STATEMENT The catalytically inactive sulfotransferase SULT4A1 may regulate the function of other SULTs by interacting with them via a conserved dimerization motif. In neuron-like cells, SULT4A1 is able to modulate dopamine toxicity by interacting with SULT1A3, potentially decreasing the metabolism of dopamine.

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