OHSU

Kirsten J. Lampi

Kirsten J. Lampi Kirsten J. Lampi, Ph.D. (1992, Oregon Health & Science U.)

Research Interests

One of the most striking observations in the aging human lens is the large amount of deamidated crystallins. Deamidation may be the most extensive post-translational modification in the human lens. Since a proposed mechanism for replacing the amide group with a carboxyl group involves the formation of a ring complex, the frequency at which deamidation occurs is surprising. The hypothesis being tested in our lab is that most of these deamidations are detrimental to the lens function. We hypothesize that deamidations decrease the stability of lens crystallins and lead to their precipitation, as we have reported for deamidation at Gln204 in bB1. Since a negative charge is introduced, deamidation can cause a dramatic change in the conformation of the protein.

To test our hypothesis, the specific aims of our research are:
  1. Determine which specific deamidations in the b-crystallins are detrimental to the lens. The effects of deamidation on conformation and stability of the b-crystallins will be determined.
  2. Determine how the changes in conformation following deamidation alter interactions of b-crystallins with other crystallins. Deamidation leading to partial unfolding may expose new surfaces on b-crystallins. This may alter interactions within b-oligomers or with other crystallins, leading to insolubilization. 
  3. Determine the mechanism for deamidations occurring in human b-crystallins. We investigate both nonenzymatic and enzymatic mechanisms for deamidation. The influence of primary and 3D structure on in vitro deamidation is examined.

These studies are important because they will help explain why crystallins become insoluble during aging and cataract formation in human lenses. Understanding how lens proteins become insoluble and scatter light, would allow drugs to be developed to delay cataracts.

Research Support

National Institutes of Health

Representative Publications

Harms MJ, Wilmarth PA, Kapfer DM, Steel EA, David LL, Bachinger HP, Lampi KJ. Laser light-scattering evidence for an altered association of beta B1-crystallin deamidated in the connecting peptide.Protein Sci. 2004 Mar;13(3):678-86.

Kim YH, Kapfer DM, Boekhorst J, Lubsen NH, Bachinger HP, Shearer TR, David LL, Feix JB, Lampi KJ. Deamidation, but not truncation, decreases the urea stability of a lens structural protein, betaB1-crystallin. Biochemistry. 2002 Nov 26;41(47):14076-84.

Mackay DS, Boskovska OB, Knopf HL, Lampi KJ, Shiels A. A nonsense mutation in CRYBB1 associated with autosomal dominant cataract linked to human chromosome 22q. Am J Hum Genet. 2002;71(5):1216-21. Epub 2002 Oct 1.

Lampi KJ, Kim YH, Bachinger HP, Boswell BA, Lindner RA, Carver JA, Shearer TR, David LL, Kapfer DM. Decreased heat stability and increased chaperone requirement of modified human betaB1-crystallins. Mol Vis. 2002 Sep 25;8:359-66.

Lampi KJ, Shih M, Ueda Y, Shearer TR, David LL. Lens proteomics: analysis of rat crystallin sequences and two-dimensional electrophoresis map.Invest Ophthalmol Vis Sci. 2002 Jan;43(1):216-24.