Cell-type specific wiring of the chaperone network

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My research program is aimed at dissecting the molecular mechanisms that allow the chaperone network to adapt to distinct and fluctuating protein folding environments in cells. Our current focus is to determine if cellular specialization (differences between cell types) modulates chaperone network function in two key aspects 1) the proteins vulnerable to misfolding and 2) the chaperones responsible for regulating specific protein misfolding targets. The human chaperone network is a cellular system composed of over 300 members that function in concert to maintain protein quality control. Chaperones recognize protein misfolding throughout the proteome and facilitate a multitude of responsive processes e.g. protein folding/refolding, sequestration of aggregates, and delivery to protein degradation systems. The chaperone network is incredibly complex; the majority of chaperones participate in numerous dynamic interactions with misfolded substrates, other chaperones, and the rest of the proteostasis machinery. Chaperone network functions regulate the folding of proteins required in all cellular processes and thus, it is critical that we decipher the underlying principles of this complex system. Human are composed of a number of distinct cell types that have specialized functions, and express the specific requisite proteins to carry out these functions. A fundamental question regarding chaperone networks is whether the system is specifically tailored to the protein quality control demands presented in a given cell type. There is evidence that expression of individual chaperones within the network varies across cell types. However, it is unknown if cell-type differences in chaperone and proteome profiles have profound effects on the pool of proteins susceptible to misfolding and the chaperones recruited to regulate specific protein misfolding targets. We will utilize iPSCs to generate three distinct cell types (undifferentiated, cardiomyocytes, neurons) in order to dissect and compare key aspects of chaperone network functions. Our first objective is to quantify proteome and chaperone network composition differences across cell types using mass spectrometry. Our second objective is to knockdown core chaperones (e.g. Hsc70, Hsp72) in all three cell types and determine 1) the protein targets susceptible to aggregation and if they are common across cell types and 2) if protein misfolding propensity within a given cell type is correlated with characteristics such as chaperone interactors, expression levels, and shared biochemical properties. Our third objective is to challenge cells with new chaperone substrates, not typically expressed in our cell types, and compare outcomes on substrate folding regulation, including the chaperones involved in these processes. Our studies will provide fundamental insights about the principles governing the relationships between the chaperone network, its substrates, and its resilience against protein folding stresses.