Kalirin promotes the exchange of GDP by GTP and stimulates the activity of specific Rho GTPases. There are several Kalirin isoforms in humans and mice. Each Kalirin isoform is composed of a unique collection of domains and may have different functions. In rat, isoforms 1 and 7 are necessary for neuronal development and axonal outgrowth, while isoform 6 is required for dendritic spine formation. In humans, the major isoform of Kalirin in the adult brain is Kalirin-7, which plays a critical role in spine formation/synaptic plasticity. Kalirin-7 has been linked to neuropsychiatric and neurological diseases such as Alzheimer's, Huntingtin's, ischemic stroke, schizophrenia, depression, and cocaine addiction.