Distinct localizations of tropomyosin isoforms in LLC-PK1 epithelial cells suggests specialized function at cell-cell adhesions

Temm-Grove, C. J., Jockusch, B. M., Weinberger, R. P., Schevzov, G., Helfman, D. M. (1998) Distinct localizations of tropomyosin isoforms in LLC-PK1 epithelial cells suggests specialized function at cell-cell adhesions. Cell Motility and the Cytoskeleton, 40 (4). pp. 393-407. ISSN 0886-1544 (Print)

Abstract

At least eight nonmuscle, nonbrain tropomyosin isoforms have been described. We used antibodies, microinjection, and transfection to characterize their expression and localization in LLC-PK1 kidney epithelial cells and compared them with other cells. Similar to primary enterocytes, LLC-PK1 cells exhibited predominantly TM-1 and TM-3 of the high-molecular-weight (HMW) isoforms; TM-5 and TM-5b of the low-molecular-weight (LMW) isoforms. Neither TM-4 nor TM-5a was detectable in the LLC-PKI cells. Immunofluorescence studies revealed that HMW isoforms were localized only on stress fibers, not adhesion belts, whereas the adhesion belts were stained by LMW isoform antibodies. When exogenous proteins are introduced either by transfection or microinjection, the HMW isoforms do not incorporate into the adhesion belt, whereas the LMW isoforms can incorporate into the stress fibers, thus indicating there are different mechanisms at work for the selective localization. Temporal changes in the microfilament system of the LLC-PK1 cells were studied during differentiation in culture as defined by spectrin expression and F-actin architecture. Western blot analysis indicated that TM-5b is only expressed in the LLC-PK1 cells after a certain degree of maturation in culture, which suggests isoform switching after the cell-cell contacts are developed. Collectively these results demonstrate that epithelial cells express a complex pattern of TM isoforms, which exhibit differential localizations within the cells and different patterns of expression depending on their origin and stage of differentiation. The implication of differential localization of TM isoforms on their specific functions is discussed.

Item Type:	Paper
Uncontrolled Keywords:	Animals Cell Adhesion Cell Differentiation Cell Polarity Colon/chemistry/cytology Epithelium/chemistry Epitopes Humans Kidney/ chemistry/cytology LLC-PK1 Cells Microvilli/chemistry Molecular Conformation Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Swine Transfection Tropomyosin/ analysis/chemistry Tumor Cells, Cultured
Subjects:	organs, tissues, organelles, cell types and functions > cell types and functions > cell functions > cell polarity organs, tissues, organelles, cell types and functions > cell types and functions > cell types > epithelial cells organs, tissues, organelles, cell types and functions > cell types and functions > cell types > epithelial cells organs, tissues, organelles, cell types and functions > cell types and functions > cell types > epithelial cells organs, tissues, organelles, cell types and functions > organs types and functions Investigative techniques and equipment > transfection
CSHL Authors:	Helfman, David M. Temm, Constanace
Communities:	CSHL labs > Helfman lab
Depositing User:	Kathleen Darby
Date:	1998
Date Deposited:	01 May 2014 13:09
Last Modified:	07 May 2014 13:03
Related URLs:	Publisher
URI:	https://repository.cshl.edu/id/eprint/29937

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