Direct binding of RalA to PKC eta and its crucial role in morphological change during keratinocyte differentiation

Shirai Yasuhito

Morioka Shoko

Sakuma Megumi

Yoshino Ken-ichi

Otsuji Chihiro

Sakai Norio

Kashiwagi Kaori

Chida Kazuhiro

Shirakawa Ryutaro

Horiuchi Hisanori

Nishigori Chikako

Ueyama Takehiko

Saito Naoaki

Molecular biology of the cell

During differentiation, keratinocytes undergo a dramatic shape change from small and round to large and flat, in addition to production of proteins necessary for the formation of epidermis. It has been shown that protein kinase C (PKC) η is crucial for keratinocyte differentiation. However, its role in this process has yet to be fully elucidated. Here, we show that catalytic activity is not necessary for enlarged and flattened morphology of human keratinocytes induced by overexpression of PKCη, although it is important for gene expression of the marker proteins. In addition, we identify the small G protein RalA as a binding partner of PKCη, which binds to the C1 domain, an indispensable region for the morphological change. The binding led activation of RalA and actin depolymerization associated with keratinocyte differentiation. siRNA techniques proved that RalA is involved in not only the keratinocyte differentiation induced by PKCη overexpression but also normal keratinocyte differentiation induced by calcium and cholesterol sulfate. These results provide a new insight into the molecular mechanism of cytoskeletal regulation leading to drastic change of cell shape.

Medical sciences [ 490 ]

eng

The American Society for Cell Biology

Copyright (c) 2011 Shirai et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution-Noncommercial-Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

[DOI] 10.1091/mbc.E10-09-0754

[NCID] AA12024500

[DOI] http://dx.doi.org/10.1091/mbc.E10-09-0754