CUTL1 Is Phosphorylated by Protein Kinase A, Modulating Its Effects on Cell Proliferation and Motility

Patrick Michl,Beate Knobel,Julian Downward

doi:10.1074/jbc.m600908200

Abstract

CUTL1, also known as CDP (CCAAT Displacement Protein), Cut, or Cux-1, is a homeodomain transcription factor known to play an essential role in development and cell cycle progression. Previously, we identified CUTL1 as modulator of cell motility and invasiveness. Here we report that protein kinase A (PKA), known to inhibit tumor progression in various tumor types, directly phosphorylates CUTL1 at serine 1215 in NIH3T3 fibroblasts. The PKA-induced phosphorylation results in decreased DNA binding affinity of CUTL1 and diminished CUTL1-mediated cell cycle progression and cell motility. Furthermore, the expression of several CUTL1 target genes involved in proliferation and migration, such as DNA polymerase A and DKK2, was modulated by PKA-induced phosphorylation. These data identify CUTL1 as a novel target of PKA through which this protein kinase can modulate tumor cell motility and tumor progression.

Highlights

Protein kinase A (PKA)2 belongs to the family of serine/threonine kinases whose activity is implicated in the regulation of a wide variety of cellular functions, such as cell metabolism, secretion, proliferation, differentiation, and neoplastic transformation [1]
CUTL1 Is Phosphorylated by PKA—By screening CUTL1 for putative phosphorylation sites using Scansite, we found several putative phosphorylation sites for PKA and protein kinase B, known as Akt
We found that the antibody recognized CUTL1 phosphorylation induced by dibutyryl-cAMP or forskolin as PKA stimulators (Fig. 1a)

Summary

Introduction

Protein kinase A (PKA) belongs to the family of serine/threonine kinases whose activity is implicated in the regulation of a wide variety of cellular functions, such as cell metabolism, secretion, proliferation, differentiation, and neoplastic transformation [1]. CAMP and protein kinase A have been shown to play a major role in the modulation of tumor progression. These effects appear to be dependent on the cellular context [3]. CUTL1, known as CDP (CCAAT displacement protein), belongs to a family of homeobox transcription factors involved in the regulation of cell growth and differentiation [10]. It is evolutionarily conserved and contains four DNA binding domains, three of which are known as Cut repeats and one as a Cut homeodomain [11]. Studies in flies indicate that the Drosophila homologue of CUTL1, Cut, is a major determinant of cell type specification downstream of the notch pathway [23] and may interact with the wingless signaling pathway [24]

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