Wan-Pin Chang

Memapsin 2 (β‐secretase) cytosolic domain binds to the VHS domains of GGA1 and GGA2: implications on the endocytosis mechanism of memapsin 2

Memapsin 2, or β‐secretase, is a membrane‐anchored aspartic protease that initiates the cleavage of β‐amyloid precursor protein (APP) leading to the production of β‐amyloid peptide in the brain and the onset of Alzheimers disease. Memapsin 2 and APP are both endocytosed into endosomes for cleavage. Here we show that the cytosolic domain of memapsin 2, but not that of memapsin 1, binds the VHS domains of GGA1 and GGA2. Gel‐immobilized VHS domains of GGA1 and GGA2 also bound to full‐length memapsin 2 from cell mammalian lysates. Mutagenesis studies established that Asp496, Leu499 and Leu500 were essential for the binding. The spacing of these three residues in memapsin 2 is identical to those in the cytosolic domains of mannose‐6‐phosphate receptors, sortilin and low density lipoprotein receptor‐related protein 3. These observations suggest that the endocytosis and intracellular transport of memapsin 2, mediated by its cytosolic domain, may involve the binding of GGA1 and GGA2.

β-Secretase inhibitor GRL-8234 rescues age-related cognitive decline in APP transgenic mice

Alzheimer disease is intimately linked to an excess amount of amyloid‐β (Aβ) in the brain. Thus, therapeutic inhibition of Aβ production is an attractive clinical approach to treat this disease. Here we provide the first direct experimental evidence that the treatment of Tg2576 transgenic mice with an inhibitor of β‐secretase, GRL‐8234, rescues the age‐related cognitive decline. We demonstrated that the injected GRL‐8234 effectively enters the brain and rapidly decreases soluble Aβ in the brain of Tg2576 mice. The rescue of cognition, which was observed only after long‐term inhibitor treatment ranging from 5 to 7.5 mo, was associated with a decrease of brain amyloid‐β plaque load. We also found no accumulation of amyloid‐β precursor protein after several months of inhibitor treatment. These observations substantiate the idea that Aβ accumulation plays a major role in the cognitive decline of Tg2576 mice and support the concept of Aβ reduction therapy as a treatment of AD.—Chang, W.‐P., Huang, X., Downs, D., Cirrito, J. R., Koelsch, G., Holtzman, D. M. Ghosh, A. K., Tang, J. β‐Secretase inhibitor GRL‐8234 rescues age‐related cognitive decline in APP transgenic mice. FASEB J. 25, 775–784 (2011). www.fasebj.org

In vivo inhibition of Aβ production by memapsin 2 (β-secretase) inhibitors

We have previously reported structure‐based design of memapsin 2 (β‐secretase) inhibitors with high potency. Here we show that two such inhibitors covalently linked to a ‘carrier peptide’ penetrated the plasma membrane in cultured cells and inhibited the production of β‐amyloid (Aβ). Intraperitoneal injection of the conjugated inhibitors in transgenic Alzheimers mice (Tg2576) resulted in a significant decrease of Aβ level in the plasma and brain. These observations verified that memapsin 2 is a therapeutic target for Aβ reduction and also establish that transgenic mice are suitable in vivo models for the study of memapsin 2 inhibition.

In vivo inhibition of Abeta production by memapsin 2 (beta-secretase) inhibitors.

We have previously reported structure‐based design of memapsin 2 (β‐secretase) inhibitors with high potency. Here we show that two such inhibitors covalently linked to a ‘carrier peptide’ penetrated the plasma membrane in cultured cells and inhibited the production of β‐amyloid (Aβ). Intraperitoneal injection of the conjugated inhibitors in transgenic Alzheimers mice (Tg2576) resulted in a significant decrease of Aβ level in the plasma and brain. These observations verified that memapsin 2 is a therapeutic target for Aβ reduction and also establish that transgenic mice are suitable in vivo models for the study of memapsin 2 inhibition.

Study of memapsin 2 (β-secretase) and strategy of inhibitor design

The discovery that β-secretase is a membrane-anchored aspartic protease memapsin 2 has stimulated much interest in the design and testing of its inhibitors for the treatment of Alzheimer’s disease. This article discusses the strategy for the development of such inhibitor drugs. Enzymology and structural determination tools have permitted the design of memapsin 2 inhibitors with high potency and in a size range possible for penetration of the blood-brain barrier. Transgenic Alzheimer’s mice have been used to show that when memapsin 2 inhibitors are transported to the brain, they effectively reduce the production of amyloid β. Although development of a clinical candidate of memapsin 2 inhibitor drug remains a very challenging undertaking, the progress so far lends some optimism for future prospects.

Erratum to: Memapsin 2 (β-secretase) cytosolic domain binds to the VHS domains of GGA1 and GGA2: implications on the endocytosis mechanism of memapsin 2 (FEBS 26327)

Erratum to: Memapsin 2 (L-secretase) cytosolic domain binds to the VHS domains of GGA1 and GGA2: implications on the endocytosis mechanism of memapsin 2 (FEBS 26327) [FEBS Letters 524 (2002) 183^187]C Xiangyuan Hea, Wan-Pin Changa, Gerard Koelscha;b, Jordan Tanga;c; aProtein Studies Program, Oklahoma Medical Research Foundation, 825 N.E. 13th Street, Oklahoma City, OK 73104, USA bZapaq, Inc., Oklahoma City, OK 73104, USA cDepartment of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA