FK506/ GDNF research update

[Guest guest]

J Neurosci. 2006 Mar 22;26(12):3335-44.

An analog of a dipeptide-like structure of FK506 increases glial cell

line-derived neurotrophic factor expression through cAMP response

element-binding protein activated by heat shock protein 90/Akt

signaling pathway.

Cen X, Nitta A, Ohya S, Zhao Y, Ozawa N, Mouri A, Ibi D, Wang L,

Suzuki M, Saito K, Ito Y, Kawagoe T, Noda Y, Ito Y, Furukawa S,

Nabeshima T.

Department of Neuropsychopharmacology and Hospital Pharmacy, Nagoya

University Graduate School of Medicine, Nagoya 466-8560, Japan.

Glial cell line-derived neurotrophic factor (GDNF) is an important

neurotrophic factor that has therapeutic implications for

neurodegenerative disorders. We previously showed that leucine-

isoleucine (Leu-Ile), an analog of a dipeptide-like structure of

FK506 (tacrolimus), induces GDNF expression both in vivo and in

vitro. In this investigation, we sought to clarify the cellular

mechanisms underlying the GDNF-inducing effect of this dipeptide. Leu-

Ile transport was investigated using fluorescein isothiocyanate-Leu-

Ile in cultured neurons, and the results showed the transmembrane

mobility of this dipeptide. By liquid chromatography-mass

spectrometry and quartz crystal microbalance assay, we identified

heat shock cognate protein 70 as a protein binding specifically to

Leu-Ile, and molecular modeling showed that the ATPase domain is the

predicted binding site. Leu-Ile stimulated Akt phosphorylation, which

was attenuated significantly by heat shock protein 90 (Hsp90)

inhibitor geldanamycin (GA). Moreover, enhanced interaction between

phosphorylated Akt and Hsp90 was detected by immunoprecipitation. Leu-

Ile elicited an increase in cAMP response element binding protein

(CREB) phosphorylation, which was inhibited by GA, indicating that

CREB is a downstream target of Hsp90/Akt signaling. Leu-Ile elevated

the levels of GDNF mRNA and protein expression, whereas inhibition of

CREB blocked such effects. Leu-Ile promoted the binding activity of

phosphorylated CREB with cAMP response element. These findings show

that CREB plays a key role in transcriptional regulation of GDNF

expression induced by Leu-Ile. In conclusion, Leu-Ile activates

Hsp90/Akt/CREB signaling, which contributes to the upregulation of

GDNF expression. It may represent a novel lead compound for the

treatment of dopaminergic neurons or motoneuron diseases.