Isoform 3 of Caldesmon

Caldesmon (CALD1) isoform 3 is a 558-amino-acid protein (64.3 kDa) that functions as a regulatory protein in the actin-myosin contractile system, modulating smooth and non-muscle cell motility and cytokinesis (UniProt: Q05682-3). The protein is widely expressed across tissues and plays roles in cytoskeletal dynamics and cellular contraction through its interaction with actin and calmodulin-binding mechanisms.

In the context of Alzheimer's disease, caldesmon isoform 3 was detected as upregulated in human post-mortem AD brain tissue compared to age-matched controls. Analysis of TMT-labeled proteomics data across four subcellular fractions (P2, P3, S2, S3) revealed a mean log2 fold-change of 1.47 (Chaparral AD proteomics), indicating increased abundance in the AD brain proteome. This upregulation was observed in one subcellular fraction analyzed, consistent with dysregulation of cytoskeletal regulatory proteins in neurodegeneration.