Download 高 茂 傑 (Mou-Chieh Kao)

高 茂 傑 (Mou-Chieh Kao)
Assistant professor
生科一館 307 室
Tel: (03)5715131 轉 42472 (office), 轉 33456 (laboratory)
E-mail: [email protected]
學歷: 美國康乃爾大學博士 (Cornell University, U.S.A.)
專長: 微生物學、生化學 (Microbiology/Biochemistry)
Academic Background
Postdoctoral Fellow (2000-2005) - The Scripps Research Institute, La Jolla, CA, U.S.A.
Ph.D. (1995-2000) - Cornell University, Ithaca, NY, U.S.A.
M.S. (1995-1998) - Cornell University, Ithaca, NY, U.S.A.
B.S. (1988-1992) - National Taiwan University, Taipei, Taiwan
Research Interests
My research interests are centered on understanding the mechanisms of complex I
and developing a strategy to reestablish the functionality of complex I thus lead to the
treatment of human mitochondrial diseases caused by the defects of this enzyme complex.
Mammalian complex I is the most intricate membrane-bound enzyme known to
date, being composed of at least 46 unlike subunits. Of these, 7 subunits are encoded by
mitochondrial DNA. It is the point of entry for the major fraction of electrons that
traverse the respiratory chain eventually resulting in the reduction of oxygen. Coupled to
the electron transfer, protons are pumped from the matrix side to the intermembrane
space of mitochondria. In contrast, the bacterial version of complex I, also called NDH-1,
is located in the plasma membrane and contains only 13 or 14 different subunits. Despite
the difference in the size and complexity, complex I and NDH-1 share many properties in
terms of structure and function.
In eukaryotes, it is not easy to manipulate mitochondrial DNA directly. In contrast,
gene manipulation procedures of bacterial DNA are well advanced. Previously, my
colleagues and I have used Paracoccus denitrificans and Escherichia coli NDH-1 as
models to study the function-structure relations of this complex and investigated the
events that are associated with pathogenic mutations of human complex I. Our
discoveries from these studies demonstrate that bacterial model systems could be useful
for further understanding of this complicated mammalian enzyme, and provide an
alternative way to gain insight into human pathogenesis derived from malfunction of this
complex. In this respect, I am interested in the following studies:
In the bacterial system:

Clarifying functional roles of amino acid residues of interest, especially those amino
acids corresponding to residues involved in human mitochondrial diseases, in the
membrane domain ND subunits of complex I

Searching proton-translocating site(s) and quinone-binding site(s)

Answering the question “Can Complex I pump not only protons but also sodium
ions?”

Determining the role of component subunits of NDH-1 in the assembly of the
complex

Using non-crystallization approaches to study subunit interactions and subunit
arrangements in complex I
Such a thorough investigation of subunit interactions and subunit arrangements
should provide clues about how electron transfer and proton translocation are coordinated
in this complicated complex. Along with answering these questions, it is my hope that the
knowledge gained through these studies will help us to have a better understanding of the
physiological-pathological dysfunction associated with human complex I diseases.
In the mammalian system:
Certainly, not every aspect of human diseases can be reflected in the bacterial
system. Therefore, a better understanding of complex I in animal mitochondria is
absolutely necessary. In this respect, I am interested in conducting studies in the
developing new strategies for studies of mitochondrially encoded complex I subunits and
for treatment of complex I dysfunction.
Recently, human complex I, especially the mitochondrially encoded subunits, has
increasing medical importance because mutations of the mtDNA have been associated
with a wide variety of human neurodegenerative diseases as well as the process of aging.
These seven mtDNA-encoded subunits of complex I are extremely hydrophobic and have
multiple membrane-spanning regions. At present no effective remedies have been
established for complex I deficiencies. Therefore, developing methods to correct complex
I defects seems important.
Gene therapy is by nature a powerful treatment method. However, a severe hurdle
in the development of mitochondrial gene therapy is that the no practical method is
currently available to transfect mammalian mitochondria with exogenous nucleic acids.
In addition, the lack of such an efficient delivery system has also made the studies of the
effects of mutations on the structure, assembly, and function of the mitochondrial
complexes extremely difficult. One possible approach to overcome the aforementioned
obstacle is to apply a so called “allotopic expression” method, in which an engineered
nucleus-localized version of an mtDNA-encoded gene is introduced to express the target
protein in the cytoplasm, and the expressed transgene-encoded protein is then posttranslationally imported into mitochondria. Several studies have to be conducted before
the above approach can be practically applied in complex I research (or other complexes
with mtDNA-encoded subunits). These studies include:

Investigating factors necessary for successful gene transfer of a hydrophobic protein
that is usually mitochondrial-encoded into the nucleus and developing a delivery
system which has high possibility for long term expression of transgenes

Considering the differences in the codon preference existing between the
mitochondrial and nuclear genomes to redesign and recode the mitochondrial genes
of interests for nuclear expression

Changing the local hydrophobicity of the subunits to facilitate the protein transfer

Surveying the use of the leader sequence as the mitochondrial targeting presequence
to direct the protein to the mitochondria to achieve the correct localization
Overcoming these challenges requires a solid knowledge of the mitochondrial
protein transport machinery. Once the correct expression of the selected, relocated
mtDNA-encoded subunit is established and the expressed subunit can restore the NADH
oxidase activity in the complex I-deficient culture cells, in vivo study utilizing the murine
model system can be followed. The final goal is to develop a promising strategy for the
treatment of human diseases caused by complex I defects. In addition, it is anticipated
that such a strategy might be applicable for therapies of dysfunction of other enzyme
complexes involved in oxidative phosphorylation.
Recent Publications
Kao, M.-C., Nakamaru-Ogiso, Matsuno-Yagi, A., and Yagi, T. (2005). “Characterization
of the membrane domain subunit NuoK (ND4L) of the NADH-quinone oxidoreductase
from Escherichia coli”. Biochemistry 44:9545-9554.
Kao, M.-C., Di Bernardo, S., Nakamaru-Ogiso, E., Miyoshi, H., Matsuno-Yagi, A., and
Yagi, T. (2005). “Characterization of the membrane domain subunit NuoJ (ND6) of the
NADH-quinone oxidoreductase from Escherichia coli by chromosomal DNA
manipulation”. Biochemistry 44:3562-3571.
Kao, M.-C., Di Bernardo, S., Perego, M., Nakamaru-Ogiso, E., Matsuno-Yagi, A., and
Yagi, T. (2004). “Functional roles of four conserved residues in the membrane domain
subunit NuoA of the proton-translocating NADH-quinone oxidoreductase from
Escherichia coli”. J. Biol. Chem. 279:32360-32366.
Kao, M.-C., Mastuno-Yagi, A., and Yagi, T. (2004) “Subunit proximity in the H+translocating NADH-quinone oxidoreductase probed by zero-length crosslinking”.
Biochemistry 43:3750-3755.
Yagi, T., Di Bernaldo, S., Nakamaru-Ogiso, E., Kao, M.-C., Seo, B.B., and MatsunoYagi, A. (2004) “NADH dehydrogenase (NADH-quinone oxidoreductase)”. In
Respiration in Archaea and Bacteria. (ed: Zannoni, D.) pp15-40, Kluwer Publishings,
Dordrecht.
Kao, M.-C., Di Bernardo, S., Matsuno-Yagi, A., and Yagi, T. (2003) Characterization
and topology of the membrane domain Nqo10 subunit of the proton-translocating
NADH-quinone oxidoreductase of Paracoccus denitrificans”. Biochemistry 42:45344543.
Kao, M.-C., Di Bernardo, S., Matsuno-Yagi, A., and Yagi, T. (2002) “Characterization
of the membrane domain Nqo11 subunit of the proton-translocating NADH-quinone
oxidoreductase of Paracoccus denitrificans”. Biochemistry 41:4377-4384.
Yagi, T., Seo, B. B., Di Bernardo, S., Nakamaru-Ogiso, E., Kao, M.-C., and MatsunoYagi, A. (2001) “NADH Dehydrogenases: From Basic Science to Biomedicine”. J.
Bioenerg. Biomembr. 33:233-242.