CALD1

CALD1 Full Name

caldesmon 1

CALD1 Introduction

The CALD1 gene encodes Caldesmon, a pivotal cytoskeleton-associated protein that acts as a modulator of actomyosin contraction and filament stability. Through alternative splicing, CALD1 produces two distinct isoforms with tissue-specific distribution: high-molecular-weight Caldesmon (H-CaD), which is restricted to smooth muscle cells, and low-molecular-weight Caldesmon (L-CaD), which is ubiquitous in non-muscle tissues.

Figure 1. The schematic structures of CaD protein isoforms, human CALD1 gene and the transcripts. (Source: Mayanagi T, et al. 2011)

Functionally, Caldesmon serves as a "brake" on cellular contraction. It binds simultaneously to actin and myosin, thereby inhibiting the actomyosin ATPase activity and preventing filament sliding in the absence of calcium. This inhibition is relieved via a Ca²⁺/calmodulin-dependent mechanism: when intracellular calcium levels rise, calcium-calmodulin binds to Caldesmon, causing it to dissociate from actin and allowing contraction to proceed. In non-muscle cells, L-CaD plays a crucial role in regulating cell shape and stabilizing stress fibers (actin bundles).

The clinical relevance of CALD1 is increasingly recognized in the field of oncology, particularly concerning tumor metastasis. While H-CaD expression is often lost during the dedifferentiation of smooth muscle tumors (leiomyosarcomas), the L-CaD isoform is frequently upregulated in various aggressive cancers, including gastric, colorectal, and breast cancers. High levels of L-CaD facilitate the remodeling of the actin cytoskeleton, which enhances the motility and invasiveness of cancer cells, allowing them to migrate and form metastases. Furthermore, because H-CaD is highly specific to smooth muscle, it serves as a valuable diagnostic immunohistochemical marker for differentiating smooth muscle tumors from other mesenchymal neoplasms in pathology.

Alternate Names for CALD1

CALD1; caldesmon 1; CDM; HCAD; LCAD; H-CAD; L-CAD; NAG22; caldesmon;

• Immunohistochemistry Antibodies for Pathology

• 1. Mayanagi T, et al. Diversification of caldesmon-linked actin cytoskeleton in cell motility. Cell Adh Migr. 2011 Mar-Apr;5(2):150-9.
  2. Yao YB, et al. Caldesmon: Biochemical and Clinical Implications in Cancer. Front Cell Dev Biol. 2021 Feb 18;9:634759.