Sorting nexin 1 (SNX1) is a member of a large family of hydrophilic proteins that interact with a variety of receptor types and are involved in intracellular trafficking (1). SNX1 and the related splice variant, SNX1A, bind the epidermal growth factor (EGF) receptor, facilitate its transport to lysosome, and thereby contribute to the degradation of the receptor (2,3). SNX2 and SNX4 share a high degree of amino acid similarity with SNX1, as they all contain a characteristic phox homology (PX

p130 is related both in structure and function to the retinoblastoma tumor suppressor protein and p107 (collectively known as pocket proteins) and is known to regulate the activity of E2F transcription factors. E2F transcription factors regulate the expression of a number of genes important in cell proliferation, particularly those involved in the progression through G1 and into the S phase of the cell cycle. Binding of p130 converts E2F transcription factors from transcriptional activators

In eukaryotes, the phosphorylation and dephosphorylation of proteins on serine and threonine residues is an essential means of regulating a broad range of cellular functions, including division, homeostasis and apoptosis. A group of proteins that are intimately involved in this process are the protein phosphatases. In general, the protein phosphatase (PP) holoenzyme is a trimeric complex composed of a regulatory subunit, a variable subunit, and a catalytic subunit. Four major families of pr