Taking Aim at the Failing
If the golden dream of molecular medicine is to treat
disease on the cellular level, what better target could there be
than the failing human heart? In heart failure, cardiomyocytes
are caught in a vicious spiral of damage, declining efficiency,
and then apoptosis or cellular suicide. As more failing
cardiomyocytes kill themselves, the heart’s ability to contract
weakens, the damage spreads, and the process accelerates.
Intervening precisely in a basic cell process such as apoptosis
would be an incredible step forward in treating heart disease.
Amazingly, the principle has already been demonstrated.
In earlier laboratory experiments using cultured heart muscle
cells, an enzyme involved in anti-apoptotic signaling, Akt ki-
nase, was delivered to the cell surface of damaged
cardiomyocytes by using the fatty acid, myristolate, as a kind
of anchor. The Akt performed beautifully, inhibiting cell death
and preventing the spread of new pathogenic signals. How-
ever, the myristolated form had undesirable side effects for
cardiac structure and function that limited its potential for
therapy. Now the cellular delivery of Akt has been further
refined. This time, an international team of Japanese and
American researchers has targeted Akt even more precisely,
using an adenovirus as the vector to aim the anti-apoptotic
kinase directly at the cell’s nucleus.
Accumulation of activated Akt in cardiomyocyte nuclei
was first discovered by Mark Sussman at the Children’s Hos-
pital Medical Center, Cincinnati. Reasoning that the nucleus
might be the biologically relevant target for Akt, Isao Shiraishi
who is now at the Children’s Research Hospital in Kyoto, Ja-
pan worked with Sussman and other collaborators at the Bos-
ton University School of Medicine and the Massachusetts
General Hospital, developing a targeted Akt construct to be
aimed at the cell nucleus. An adenovirus turned out to be the
ideal vehicle to deliver the targeted Akt gene.
After confirming by confocal microscopy and
immunoblot analysis the safe delivery of their Akt construct,
the researchers checked for signs of morphological damage
and found none. They did find significantly higher levels of
Akt in the nuclei of targeted cells compared to controls that
received an adenovirus delivering an irrelevant nuclear-tar-
geted protein. Shiraishi and colleagues then subjected their
nuclear-targeted cells to the insults of hypoxia (low oxygen)
and hypoglycemia (low glucose). The nuclear-targeted
cardiomyocytes resisted as strongly as those that had received
the myristolated Akt, but without the side effects. In all, it
was an amazing shot and a possible preview of a new kind of
treatment to be delivered where it will do the most good.
Contact: Mark Sussman, Children’s Hospital Medical
Center, Division of Molecular Cardiovascular Biology, Room
3033, 3333 Burnet Avenue, Cincinnati, OH 45229-3039,
Isao Shiraishi, Children’s
Research Hospital, Kyoto Prefectural University of Medi-
cine, Division of Pediatrics, Kawaramachi-Hirokoji.
Kamigyo-ku, Kyoto, 602-8566, Japan, 81-75-251-5832,
Nuclear Targeting of Akt Enhances Kinase Activity and Sur-
vival of Cardiomyocytes.
Molecular and Cardiovascular Biology, Children’s
Hospital Medical Center, Cincinnati, OH,
Division of Pedi-
atrics, Children’s Research Hospital, Kyoto Prefectural Uni-
versity of Medicine, Kyoto, Japan,
Whitaker Cardiovascular/Molecular Car-
diology, Boston University School of Medicine, Boston, MA,
Program in Cardiovascular Gene Therapy, Cardiovascular Re-
search Center, Massachusetts General Hospital, Harvard
Medical School, Boston, MA
At the ASCB Meeting: Program 915, Poster B86, Apoptosis
II. Author presents: Monday, December 16, 1:30—3:00 PM.
THE AMERICAN SOCIETY FOR CELL BIOLOGY
42ND ANNUAL MEETING
December 14-18, 2002, San Francisco, CA
Cardiomyocyte cultures infected with adenovirus expressing nuclear-
targeted Akt kinase. Cells are labeled with texas-red phalloidin to decorate
actin filaments (in red) as well as anti-Akt antibody to detect expression of
Akt protein (green). Numerous labeled nuclei throughout the field show
efficient expression and targeting of the virally-encoded Akt kinase.