Role of Ca 2+} activation and bilobal structure of calmodulin in nuclear and nucleolar localization

Richard Thorogate , Katalin Török (1)

1 Basic Medical Sciences

Ca 2+} signaling to the nucleus is thought to occur by calmodulin entry into the nucleus where calmodulin has many functions. We investigated the role of Ca 2+} and the N- and C-terminal lobes of calmodulin in its subnuclear targeting by using fluorescently labeled calmodulin and its mutants and confocal microscopy. Our data show, firstly, that Ca 2+} stimulation induces a reorganization of subnuclear structures to which apo-calmodulin can bind. Secondly, Ca 2+}-independent association of the C-terminal lobe is seen with subnuclear structures such as chromatin, the nuclear envelope and the nucleoli. Thirdly, Ca 2+}-dependent accumulation of both calmodulin and the C-terminal calmodulin lobe occurs in the nucleoli. The N-terminal lobe of calmodulin does not show significant binding to subnuclear structures although similarly to the C-terminal lobe, it accumulates in the nucleoplasm of wheat germ agglutinin-blocked nuclei suggesting that a facilitated nuclear export mechanism exists for calmodulin.

Mots clés: Life Sciences

Richard Thorogate, Katalin Török. Role of Ca 2+} activation and bilobal structure of calmodulin in nuclear and nucleolar localization. Biochemical Journal, 2006, 402 (1), pp.71-80. ⟨10.1042/BJ20061111⟩. ⟨hal-00478637⟩