A method for treating a disease caused by protein retention in the endoplasmic reticulum (ER) with a sarcoplasmic/endoplasmic reticulum calcium ATPase pump inhibitor encapsulated in a polymer nanoparticle. The polymer nanoparticle is surface-modified such that it is targeted to the ER. The inhibitor reduces protein retention in the ER and the encapsulation lowers side effects of the inhibitor, e.g., cytotoxicity, as compared to administering the inhibitor without encapsulation. Also disclosed is a pharmaceutical composition that can be used for carrying out the method. Further provided is a transgenic mouse carrying in its genome a heterologous nucleic acid that encodes an H338Y mutant gp91phox protein. The transgenic mouse can serve as a model for human chronic granulomatous disease.
