Kinesin-associated protein 3

Kinesin-associated protein 3 (KIFAP3, also known as KAP3) is a 792-amino-acid protein that functions as a regulatory component of the KIF3 motor complex (UniProt: Q92845). It binds to the tail domain of the KIF3A/KIF3B heterodimer to form a functional heterotrimeric complex, regulating membrane binding and supporting cellular processes including chromosome tethering to the spindle pole and chromosome movement during cell division.

KIFAP3 is expressed across human tissues and participates in microtubule-based motor protein function, a process fundamental to axonal transport and cellular organization in neurons. While no primary disease association is documented in UniProt, the protein's role in microtubule dynamics implicates it in pathways relevant to neuronal health.

In Alzheimer's disease, KIFAP3 shows reduced abundance in post-mortem AD brain tissue compared to age-matched controls, with a mean log2 fold-change of −0.55 across subcellular fractions (Chaparral AD proteomics). This downregulation suggests impaired kinesin-mediated transport capacity in the AD brain, potentially contributing to the axonal dysfunction and neurodegeneration characteristic of the disease.