A novel interaction of CLN3 with nonmuscle myosin-IIB and defects in cell motility of Cln3 cells

Juvenile neuronal ceroid lipofuscinosis (JNCL) is a pediatric lysosomal storage disorder characterized by accumulation of autofluorescent storage material and neurodegeneration, which result from mutations in CLN3. The function of CLN3, a lysosomal membrane protein, is currently unknown. We report that CLN3 interacts with cytoskeleton-associated nonmuscle myosin-IIB. Both CLN3 and myosin-IIB are ubiquitously expressed, yet mutations in either produce dramatic consequences in the CNS such as neurodegeneration in JNCL patients and Cln3^−/− mouse models, or developmental deficiencies in Myh10^−/− mice, respectively. A scratch assay revealed a migration defect associated with Cln3^−/− cells. Inhibition of nonmuscle myosin-II with blebbistatin in WT cells resulted in a phenotype that mimics the Cln3^−/− migration defect. Moreover, inhibiting lysosome function by treating cells with chloroquine exacerbated the migration defect in Cln3^−/−. Cln3^−/− cells traversing a transwell filter under gradient trophic factor conditions displayed altered migration, further linking lysosomal function and cell migration. The myosin-IIB distribution in Cln3^−/− cells is elongated, indicating a cytoskeleton defect caused by the loss of CLN3. In summary, cells lacking CLN3 have defects that suggest altered myosin-IIB activity, supporting a functional and physical interaction between CLN3 and myosin-IIB. We propose that the migration defect in Cln3^−/− results, in part, from the loss of the CLN3–myosin-IIB interaction.