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Role of Scd5, a protein phosphatase-1 targeting protein, in phosphoregulation of Sla1 during endocytosis
Richard J. Chi, Onaidy T. Torres, Verónica A. Segarra, Tanya Lansley, Ji Suk Chang, Thomas M. Newpher, Sandra K. Lemmon


Phosphorylation regulates assembly and disassembly of proteins during endocytosis. In yeast, Prk1 and Ark1 phosphorylate factors after vesicle internalization leading to coat disassembly. Scd5, a protein phosphatase-1 (PP1)-targeting subunit, is proposed to regulate dephosphorylation of Prk1/Ark1 substrates to promote new rounds of endocytosis. In this study we analyzed scd5-PP1Δ2, a mutation causing impaired PP1 binding. scd5-PP1Δ2 caused hyperphosphorylation of several Prk1 endocytic targets. Live-cell imaging of 15 endocytic components in scd5-PP1Δ2 revealed that most factors arriving before the invagination/actin phase of endocytosis had delayed lifetimes. Severely affected were early factors and Sla2 (Hip1R homolog), whose lifetime was extended nearly fourfold. In contrast, the lifetime of Sla1, a Prk1 target, was extended less than twofold, but its cortical recruitment was significantly reduced. Delayed Sla2 dynamics caused by scd5-PP1Δ2 were suppressed by SLA1 overexpression. This was dependent on the LxxQxTG repeats (SR) of Sla1, which are phosphorylated by Prk1 and bind Pan1, another Prk1 target, in the dephosphorylated state. Without the SR, Sla1ΔSR was still recruited to the cell surface, but was less concentrated in cortical patches than Pan1. sla1ΔSR severely impaired endocytic progression, but this was partially suppressed by overexpression of LAS17, suggesting that without the SR region the SH3 region of Sla1 causes constitutive negative regulation of Las17 (WASp). These results demonstrate that Scd5/PP1 is important for recycling Prk1 targets to initiate new rounds of endocytosis and provide new mechanistic information on the role of the Sla1 SR domain in regulating progression to the invagination/actin phase of endocytosis.


  • *Present address: Department of Cell Biology, Yale University, New Haven, CT 06510, USA

  • ‡Present address: Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA

  • Present address: Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA

  • Funding

    This work was supported by the National Institutes of Health [grant numbers T32-HL07188 and 5F32-GM087900 to R.J.C, T32-HL007188 to T.L., R01-GM055796 to S.K.L.]. Deposited in PMC for release after 12 months.

  • Supplementary material available online at

  • Accepted June 18, 2012.
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