AJP - Cell Physiology, Vol 270, Issue 5 C1532-C1543, Copyright © 1996 by American Physiological Society

ARTICLES

Nuclear ion channel activity is regulated by actin filaments

A. G. Prat and H. F. Cantiello
Renal Unit, Massachusetts General Hospital East, Charlestown 02129, USA.

Actin filaments are novel second messengers involved in ion channel regulation. Because cytoskeletal components interact with the nuclear envelope, the actin cytoskeleton may also control nuclear membrane function. In this report, the patch-clamp technique was applied to isolated nuclei from amphibian A6 epithelial cells to assess the role of actin filaments on nuclear ion channel activity under nucleus-attached or -excised conditions. The most prevalent spontaneous nuclear ion channel species, 76% (n = 46), was cation selective and had a maximal single-channel conductance of approximately 420 pS. Nuclear ion channels also displayed multiple subconductance states, including channel activity of 26 pS that was frequently observed. Nuclear ion channel activity on otherwise quiescent patches was induced by either addition of the actin cytoskeleton disrupter cytochalasin D (CD; 5 micrograms/ml, 60%, 3 of 5 patches) or actin (10-1,000 micrograms/ml) to the bathing solution of nucleus-attached patches (59%, 13 of 22 patches). Actin also induced ion channel activity in quiescent excised inside-out patches from the nuclear envelope (80%, 4 of 5 patches). In contrast, addition of bovine serum albumin (10-1,000 micrograms/ml) to the bathing solution of nucleus-attached patches was without effect on nuclear ion channel activity (5 of 5 patches). The monoclonal antibody MAb414, specific for nuclear pore complex proteins, completely prevented either spontaneous or cytosolic actin-induced nuclear ion channels under nucleus-attached conditions (4 of 4 patches) but not intranuclear actin-induced nuclear ion channels under excised inside-out conditions (3 of 3 patches). In nucleus-attached patches, channel activity was readily activated by addition of the G-actin-binding protein deoxyribonuclease I to nucleus-attached patches (56%, 5 of 9 patches) or further addition of the actin-cross-linker filamin in the presence of actin (57%, 4 of 7 patches). The data indicate that dynamic changes in actin filament organization may represent a novel mechanism to control nuclear function.

This article has been cited by other articles:

				V. SHAHIN, T. DANKER, K. ENSS, R. OSSIG, and H. OBERLEITHNER Evidence for Ca2+- and ATP-sensitive peripheral channels in nuclear pore complexes FASEB J, September 1, 2001; 15(11): 1895 - 1901. [Abstract] [Full Text] [PDF]

				M. Mazzanti, J. O. Bustamante, and H. Oberleithner Electrical Dimension of the Nuclear Envelope Physiol Rev, January 1, 2001; 81(1): 1 - 19. [Abstract] [Full Text] [PDF]

				T. Danker, H. Schillers, J. Storck, V. Shahin, B. Kramer, M. Wilhelmi, and H. Oberleithner Nuclear hourglass technique: An approach that detects electrically open nuclear pores in Xenopus laevis oocyte PNAS, November 9, 1999; 96(23): 13530 - 13535. [Abstract] [Full Text] [PDF]

				A. H. van der Luit, C. Olivari, A. Haley, M. R. Knight, and A. J. Trewavas Distinct Calcium Signaling Pathways Regulate Calmodulin Gene Expression in Tobacco Plant Physiology, November 1, 1999; 121(3): 705 - 714. [Abstract] [Full Text]

				R. TONINI, F. GROHOVAZ, C. A. M. LAPORTA, and M. MAZZANTI Gating mechanism of the nuclear pore complex channel in isolated neonatal and adult mouse liver nuclei FASEB J, August 1, 1999; 13(11): 1395 - 1403. [Abstract] [Full Text]