CD98hc (SLC3A2) Interaction with the Integrin β Subunit Cytoplasmic Domain Mediates Adhesive Signaling

Gerald W Prager,Chloé C Féral,Chungho Kim,Jaewon Han,Mark H Ginsberg

doi:10.1074/jbc.m702877200

Gerald W Prager, Chloé C Féral + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m702877200

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Abstract

In mammals, beta1 integrin adhesion receptors generate signals that mediate cell spreading, migration, proliferation, and survival. CD98, a heterodimeric transmembrane protein, physically associates with certain integrin beta subunit cytoplasmic domains (tails) via its heavy chain, CD98hc (SLC3A2), and loss of CD98hc impairs integrin signaling. Here we have used the lack of CD98hc interaction with the Drosophila integrin betaPS tail for a homology scanning analysis that implicated the C-terminal 8 residues of beta3 (Thr(755)-Thr(802)) in CD98hc binding. We then identified point mutations in the beta3 C terminus (T755K and T758M) that abolish CD98hc association and a double mutation in the corresponding residues in the betaPS tail (K839T,M842T), which resulted in gain of CD98hc interaction. Furthermore, the loss of function beta3(T755K) mutation or the gain of function beta3/betaPS(K839T,M842T) led to a loss or gain of integrin-mediated cell spreading, respectively. Thus, we have identified critical integrin residues required for CD98hc interaction and in doing so have shown that CD98c interaction with the integrin beta tail is required for its ability to mediate integrin signaling. These studies also provide new insights into how CD98hc may cooperate with other cytoplasmic domain binding proteins to modulate integrin functions and into the evolution of integrin signaling.

Highlights

Signaling by interacting with cytoplasmic proteins [9]
A genetic complementation strategy identified an interaction between a transmembrane protein, CD98, and the integrin ␤1A cytoplasmic domain [10], suggesting that this interaction might participate in integrin signaling
Using loss of function and gain of function mutants at these residues, we find that CD98hc binding to integrin ␤ tails is required for efficient adhesion-dependent cell spreading

Summary

Introduction

Signaling by interacting with cytoplasmic proteins [9]. In addition, a genetic complementation strategy identified an interaction between a transmembrane protein, CD98, and the integrin ␤1A cytoplasmic domain [10], suggesting that this interaction might participate in integrin signaling. The CD98hc intracellular domain is necessary and sufficient for interaction with integrins and promotion of integrin signaling [12, 16], whereas the CD98hc extracellular domain interacts with the light chains to promote amino acid transport [12]. Authentic CD98hc orthologues are not evident in invertebrates [17], and we report that an invertebrate ␤ integrin cytoplasmic domain, Drosophila ␤PS, fails to bind mammalian CD98hc. We use this species difference and a “homology scanning” strategy to identify two residues in the integrin ␤ tail that control the binding specificity for CD98hc but have no effect on talin binding. We show that the interaction of CD98hc with the integrin ␤ subunit tail mediates adhesive signaling

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