A Myristoyl-Binding Site in the SH3 Domain Modulates c-Src Membrane Anchoring

Anabel-Lise Le Roux,Irrem-Laareb Mohammad,Borja Mateos,Miguel Arbesú,Margarida Gairí,Farman Ali Khan,João M.C Teixeira,Miquel Pons

doi:10.1016/j.isci.2019.01.010

Anabel-Lise Le Roux, Irrem-Laareb Mohammad + Show 6 more

Open Access

https://doi.org/10.1016/j.isci.2019.01.010

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Abstract

SummaryThe c-Src oncogene is anchored to the cytoplasmic membrane through its N-terminal myristoylated SH4 domain. This domain is part of an intramolecular fuzzy complex with the SH3 and Unique domains. Here we show that the N-terminal myristoyl group binds to the SH3 domain in the proximity of the RT loop, when Src is not anchored to a lipid membrane. Residues in the so-called Unique Lipid Binding Region modulate this interaction. In the presence of lipids, the myristoyl group is released from the SH3 domain and inserts into the lipid membrane. The fuzzy complex with the SH4 and Unique domains is retained in the membrane-bound form, placing the SH3 domain close to the membrane surface and restricting its orientation. The apparent affinity of myristoylated proteins containing the SH4, Unique, and SH3 domains is modulated by these intramolecular interactions, suggesting a mechanism linking c-Src activation and membrane anchoring.

Highlights

INTRODUCTION cSrc is the leading member of the Src family of kinases (SFK)
C-Src has been associated to a plethora of cell signaling pathways and has emerged as a key player in the regulation of cell adhesion, growth, movement, differentiation, and cell invasion and survival. c-Src deregulation is directly associated to poor prognosis in colorectal and breast cancer (Martin, 2001; Yeatman, 2004; Sen and Johnson, 2011; Sirvent et al, 2012). c-Src shares with the other SFKs a common domain arrangement formed by the membrane-anchoring SH4 region followed by the Unique domain (UD), and the SH3, SH2, and kinase domains
We found that the N-terminal myristoyl group binds to the SH3 domain in free c-Src

Summary

Introduction

INTRODUCTION cSrc is the leading member of the Src family of kinases (SFK). Its oncogenic potential was brought to light already in 1970 (Duesberg and Vogt, 1970). C-Src shares with the other SFKs a common domain arrangement formed by the membrane-anchoring SH4 region followed by the Unique domain (UD), and the SH3, SH2, and kinase domains. The SH3, SH2, and kinase domains can adopt a closed, autoinhibited form stabilized by interactions between the SH2 domain and a phosphotyrosine residue near the C terminus, as well as additional interactions involving the SH3 domain (Xu et al, 1999). A second lipid interaction motif is required for effective membrane anchoring. This is provided by palmitoylation of cysteine residues in most SFKs and by electrostatic interaction of the positively charged SH4 domain with the negatively charged lipids in the case of c-Src (Murray et al, 1998)

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