Article

Proteolytic Cleavage and Nuclear Translocation of Fibrocystin Is Regulated by Intracellular Ca2+ and Activation of Protein Kinase C

University of Texas at Dallas, Richardson, Texas, United States
Journal of Biological Chemistry (Impact Factor: 4.57). 12/2006; 281(45):34357-64. DOI: 10.1074/jbc.M606740200
Source: PubMed

ABSTRACT Fibrocystin, a type I membrane protein of unknown function, is the protein affected in the autosomal recessive form of polycystic kidney disease. Here we show that fibrocystin undergoes regulated proteolysis. Several proteolytic cleavages occur within the predicted ectodomain, whereas at least one cleavage occurs within the cytoplasmic portion. The latter generates a C-terminal intracellular fragment that harbors the nuclear localization signal KRKVSRLAVTGERTATPAPKIPRIT and translocates to the nucleus. Proteolytic cleavage of fibrocystin occurs constitutively in long term cultures of polarized inner medullary collecting duct cells (mIMCD-3). Activation of protein kinase C and release of intracellular Ca2+ are required for proteolysis under these conditions. In short term cultures of human embryonic kidney 293 cells (HEK-293), proteolytic cleavage of fibrocystin can be elicited by stimulation of intracellular Ca2+ release or activation of protein kinase C. These results identify a novel Ca2+-dependent pathway that signals from fibrocystin located in the cell membrane to the nucleus.

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    • "In addition to the expected upper higher molecular weight one, the lower molecular weight band had an identical migration pattern to that in hICD-transfected cells (Figure 1A). This result is consistent with the finding that hICD can be cleaved from full-length FPC [14], [15] and the size of the cleaved C-tail is similar to that of hICD. In order to study the function of the cleaved fragment, we established four mIMCD-3 cell lines stably expressing hICD (Figure 1B, C). "
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    • "In contrast to recombinant fibrocystin that is post-translationally processed into multiple peptide fragments (Hiesberger et al., 2006; Kaimori et al., 2007), the bulk of the endogenous mouse protein is cleaved once in both cell lines (Figure 1D). Based on size and reactivity with two newly developed fibrocystin antibodies, the endogenous protein is apparently digested at an extracellular domain site previously identified in the recombinant protein (Figure 1C and D) (Hiesberger et al., 2006). The Oak Ridge Polycystic Kidney (ORPK) mouse model of ARPKD involves an intraflagellar transport protein necessary for ciliogenesis (Yoder et al., 2002). "
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