Paxillin Isoforms in Mouse: LACK OF THE γ ISOFORM AND DEVELOPMENTALLY SPECIFIC β ISOFORM EXPRESSION

Yuichi Mazaki,Hiroshi Uchida,Okio Hino,Shigeru Hashimoto,Hisataka Sabe

doi:10.1074/jbc.273.35.22435

Yuichi Mazaki, Hiroshi Uchida + Show 3 more

Open Access

https://doi.org/10.1074/jbc.273.35.22435

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Abstract

Paxillin, a focal adhesion protein, exists as multiple isoforms in humans (alpha, beta, and gamma). To understand more about the physiological role of each isoform, we have employed the mouse system. We found that although the alpha and beta isoforms are present in the mouse, the gamma isoform is not. The alpha isoform protein was detected clearly in most adult tissues, whereas the beta isoform protein was almost undetectable except in spleen, testis, thymus, and lung. On the other hand, mRNAs of both isoforms were detectable in all tissues we examined. High levels of the beta isoform protein was detected in peritoneal exudate macrophage cells in adult mouse as well as in cultured fibroblasts, together with the alpha isoform. The alpha isoform was expressed at a constant level throughout the embryonic stages we examined, whereas the beta isoform protein was detected at the mid-stages of development and increased to levels almost equal to those of the alpha isoform during the late stages of embryogenesis. Therefore, unlike the alpha isoform, expression of the beta isoform protein is restricted in adult tissues. Moreover, we showed that alpha and beta isoforms were colocalized within the same focal adhesion plaques, and cytoplasmic pools of both isoforms exist in the perinuclear area, colocalized with the Golgi apparatus.

Highlights

Paxillin, a focal adhesion protein, exists as multiple isoforms in humans (␣, ␤, and ␥)
The ␣ isoform was expressed at a constant level throughout the embryonic stages we examined, whereas the ␤ isoform protein was detected at the mid-stages of development and increased to levels almost equal to those of the ␣ isoform during the late stages of embryogenesis
We have shown in this paper that the mouse genome encodes the ␣ and ␤ isoforms of paxillin but not the ␥ isoform

Summary

Paxillin Isoforms in Mouse

Yuichi Mazaki‡§, Hiroshi Uchida‡¶, Okio Hinoʈ, Shigeru Hashimoto‡§, and Hisataka Sabe‡§** ‡‡. A focal adhesion protein, exists as multiple isoforms in humans (␣, ␤, and ␥). High levels of the ␤ isoform protein was detected in peritoneal exudate macrophage cells in adult mouse as well as in cultured fibroblasts, together with the ␣ isoform. Paxillin binds directly to signal transducers of protein tyrosine kinases such as focal adhesion kinase [5, 6] and c-Src [7], and is tyrosine phosphorylated upon cell to substratum adhesion [8], creating the binding sites for the Src homology 2 domains of Csk and Crk (9 –11). Human cancer cells and monoblast cells cultured in vitro have been shown to express these isoforms simultaneously. We examined the expression of paxillin protein isoforms in adult and embryonic tissues and their subcellular localization. The possible biological relevance of the difference in the ␥ isoform between human and mouse is discussed

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