We propose to continue our studies o the regulation of cellular processes by protein phosphorylation, particularly on the structure, function and regulation of protein tyrosine phosphatase (PTPs). The PTPs are now known to represent a large and diverse family of intracellular and receptor-linked enzymes. It can be assumed they play an essential role in regulating the multiplicity of events initiated by those hormone and growth factor receptors possessing intrinsic protein tyrosine kinase activity and in fine-tuning the highly integrated circuits that regulate eukaryotic cells. Our main goal is to study: a) structure, properties and regulation of the intracellular and receptor-linked enzymes; b) interplay that must exist between tyrosine and serine and threonine phosphorylation; c) subcellular localization of the PTPs and their involvement in the cell cycle and cytoskeleton reorganization; and d) their possible function in blocking or reversing cell transformation. A hypothesis attempting to explain how phosphatases might act synergistically with the kinases to elicit a full physiological response, irrespective of the state of phosphorylation of the target protein, will be tested.
