title: Differential inhibition of Hsc70 activities by two Hsc70-binding peptides.
abstract: The ability of two high-affinity Hsc70-binding peptides [FYQLALT (peptide-Phi) and NIVRKKK (peptide-K)] to differentially inhibit Hsc70-dependent processes in rabbit reticulocyte lysate (RRL) was examined. Both peptide-Phi and peptide-K inhibited chaperone-dependent renaturation of luciferase in RRL. Peptide-Phi, but not peptide-K, blocked Hsp90/Hsc70-dependent transformation of the heme-regulated eIF2 alpha kinase (HRI) into an active, heme-regulatable kinase. In contrast, peptide-K, but not peptide-Phi, inhibited Hsc70-mediated suppression of the activation of mature-transformed HRI. Furthermore, HDJ2 (Human DnaJ homologue 2), but not HDJ1, potentiated the ability of Hsc70 to suppress the activation of HRI in RRL. Mechanistically, peptide-K inhibited, while peptide-Phi enhanced, HDJ2-induced stimulation of Hsc70 ATPase activity in vitro. The data presented support the hypotheses that peptide-Phi acts to inhibit Hsc70 function by binding to the hydrophobic peptide-binding cleft of Hsc70, while peptide-K acts through binding to a site that modulates the interaction of Hsc70 with DnaJ homologues. Overall, the data indicate that peptide-Phi and peptide-K have differential effects on Hsc70 functions under quasi-physiological conditions in RRL, and suggest that therapeutically valuable peptide mimetics can be designed to inhibit specific functions of Hsc70.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078-3035, USA.
authors.forename: Vanitha
authors.initials: V
authors.lastname: Thulasiraman
authors.forename: Bo-Geon
authors.initials: BG
authors.lastname: Yun
authors.forename: Sheri
authors.initials: S
authors.lastname: Uma
authors.forename: Yan
authors.initials: Y
authors.lastname: Gu
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Scroggins
authors.forename: Robert L
authors.initials: RL
authors.lastname: Matts
mesh_terms: D000595:Amino Acid Sequence; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D017510:Protein Folding
chemical_list: D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D010455:Peptides; D008156:Luciferases