The selective recycling of lipids and proteins is critical to healthy cellular function. Many genes associated with human diseases encode components of the cellular machinery that sorts lipids and proteins for selective trafficking along endocytotic pathways leading to lysosomal degradation. Dr. Puertollano seeks to understand precisely how defects in intracellular trafficking—specifically, in endosomal/lysosomal pathways—contribute to human diseases.
The current focus of her work is the function of mucolipins, a novel family of ion channels that belongs to the superfamily of transient receptor potential (TRP) channels. In mammals, the mucolipin family includes three members, mucolipin-1, -2, and -3 (MCOLN1-3), which share approximately 75% amino acid similarity. Loss-of-function mutations of human MCOLN1 result in mucolipidosis type IV (MLIV), a lysosomal storage disorder characterized by severe neurological and ophthalmologic abnormalities. Meanwhile, gain-of-function mutations in mouse MCOLN3 cause the varitint-waddler phenotype that shows pigmentation and hearing defects. Thus, MCOLNs play an important role in cellular function yet their properties and functions are not completely understood.
By using a combination of biochemistry, confocal, and electronic microscopy, Dr. Puertollano has found that MCOLNs are located to endosomes and lysosomes, where they appear to regulate changes in the luminal ion composition of endosomal organelles. Well-regulated storage and release of ions, like calcium, is clearly important for membrane trafficking and signaling, but little is known about the regulation of ion concentration within endosomal organelles. To gain better understanding, Dr. Puertollano has extended her in vitro studies of MCOLNs to animal models using genetic approaches in zebrafish and mice. Her goal is to uncover pathological cascades beginning with alterations in basic homeostatic mechanisms of intracellular compartments that may be common to many diseases.
Another major interest in Dr. Puertollano’s laboratory is the characterization of the molecular mechanisms that regulate the localization and activity of TFEB and TFE3, two members of the basic helix-loop-helix leucine-zipper family of transcription factors that control expression of autophagic, lysosomal, and metabolic genes. Dr. Puertollano is exploring the role of lysosomes as signaling centers critical for the cellular adaptation to a variety of stress conditions, including nutrient deprivation, protein misfolding, and pathogen infection; as well as the use of TFEB and TFE3 as therapeutic targets for the treatment of neurological and lysosomal diseases.