Article

Rab27 effector Slp2-a transports the apical signaling molecule podocalyxin to the apical surface of MDCK II cells and regulates claudin-2 expression.

Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Miyagi, Japan.
Molecular biology of the cell (impact factor: 5.98). 07/2012; 23(16):3229-39. DOI:10.1091/mbc.E12-02-0104 pp.3229-39
Source: PubMed

ABSTRACT Most cells in tissues are polarized and usually have two distinct plasma membrane domains-an apical membrane and a basolateral membrane, which are the result of polarized trafficking of proteins and lipids. However, the mechanism underlying the cell polarization is not fully understood. In this study, we investigated the involvement of synaptotagmin-like protein 2-a (Slp2-a), an effector molecule for the small GTPase Rab27, in polarized trafficking by using Madin-Darby canine kidney II cells as a model of polarized cells. The results show that the level of Slp2-a expression in MDCK II cells increases greatly as the cells become polarized and that its expression is specifically localized at the apical membrane. The results also reveal that Slp2-a is required for targeting of the signaling molecule podocalyxin to the apical membrane in a Rab27A-dependent manner. In addition, ezrin, a downstream target of podocalyxin, and ERK1/2 are activated in Slp2-a-knockdown cells, and their activation results in a dramatic reduction in the amount of the tight junction protein claudin-2. Because both Slp2-a and claudin-2 are highly expressed in mouse renal proximal tubules, Slp2-a is likely to regulate claudin-2 expression through trafficking of podocalyxin to the apical surface in mouse renal tubule epithelial cells.

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Keywords

activation results
 
apical membrane
 
apical surface
 
basolateral membrane
 
claudin-2 expression
 
dramatic reduction
 
effector molecule
 
junction protein claudin-2
 
Madin-Darby canine kidney II cells
 
MDCK II cells increases
 
mouse renal proximal tubules
 
mouse renal tubule epithelial cells
 
polarized cells
 
polarized trafficking
 
Rab27A-dependent manner
 
signaling molecule podocalyxin
 
Slp2-a expression
 
Slp2-a-knockdown cells
 
small GTPase Rab27
 
synaptotagmin-like protein 2-a