The long-term objective of this proposal is to develop a detailed understanding of the role of specific Ca/2+ pumps in cardiovascular and pulmonary physiology in vivo. The Ca/2+-transporting ATPases being studied are the sarco(endo)plasmic reticulum Ca/2+-ATPases (SERCAs), which sequester Ca/2+ in intracellular storage organelles, and the plasma membrane Ca/2+-ATPases (PMCAs), which extrude Ca/2+ from the cell. It is clear that SERCAs and PMCAs serve as effector molecules controlling critical aspects of Ca/2+ homeostasis and signaling, and excitation- contraction coupling in muscle; however, the specific roles of individual isoforms are poorly understood. To obtain this information we are developing mouse models with mutations in each of the Ca/2+ pumps. We have prepared mice with SERCA2, SERCA3, and PMCA2 null mutations, and have demonstrated defective cardiac function in SERCA2 heterozygous mutants and defective endothelium and epithelium dependent relaxation of vascular and pulmonary smooth muscle in SERCA3 null mutants.
In aim 1 we will develop mice with null mutations in the PMCA1 and PMCA4 genes, and will also develop a mouse with a modified PMCA1 gene that will produce only the ubiquitous PMCA1b variant, and not the variants with an acidic calmodulin binding domain that are restricted to excitable tissues. These experiments will test the general hypotheses that individual Ca/2+ pumps serve essential housekeeping on organ-specific functions, and may reveal unexpected phenotypes that yield insights regarding the specific functions of these pumps.
In aim 2 we will analyze the developmental and histopathological consequences of mutations in each of the Ca/2+ pumps, and will perform studies using both the intact animal and isolated tissues to assess the physiological role of these pumps in cardiovascular and pulmonary tissues. These experiments will test the hypotheses that SERCA and PMCA pumps regulate cardiac contractility and pulmonary and vascular smooth muscle tone and contractility, which in turn affects cardiac function, airway resistance, and arterial blood pressure. We anticipate that the six mutant mouse lives developed in this proposal will become valuable models for analysis of the mechanisms by which Ca/2+-transporting ATPases modulate physiological functions of cardiovascular, pulmonary, and other tissues.
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