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Desquamin is an epidermal ribonuclease
P Selvanayagam1, G Lei, T Bell
1Department of Pathology, University of Texas Medical Branch, Galveston 77555, USA.
Journal of Cellular Biochemistry
|January 4, 1998
Summary
Desquamin, a glycoprotein from human epidermis, degrades nuclear material in cultured keratinocytes. This enzyme exhibits specific ribonuclease activity, targeting cytosine residues in RNA but not DNA.
Area of Science:
- Biochemistry
- Cell Biology
- Dermatology
Background:
- Desquamin is a glycoprotein found in the upper granular layer and stratum corneum of human epidermis.
- Terminal differentiation in submerged keratinocyte cultures does not typically form these epidermal layers.
Purpose of the Study:
- To investigate the function and enzymatic activity of desquamin.
- To determine desquamin's effect on cultured keratinocytes and its potential nuclease activity.
Main Methods:
- Exogenous addition of desquamin to human cultured keratinocytes.
- In situ lysis of cultured cells followed by incubation with desquamin and hematoxylin staining.
- Assay of ribonuclease activity using human epidermal total RNA and synthetic RNA homopolymers.
- Agarose/formaldehyde gel electrophoresis to monitor RNA degradation.
- Testing for DNA degradation.
Main Results:
- Desquamin extended keratinocyte maturation and caused a loss of cell nuclei.
- Incubation with desquamin degraded the basophilic nuclear matrix while nuclear inclusions remained intact.
- Desquamin demonstrated dose-dependent ribonuclease activity specific to RNA, particularly at cytosine residues.
- Desquamin did not degrade DNA.
Conclusions:
- Desquamin possesses nuclease activity, specifically targeting RNA.
- The enzyme plays a role in nuclear material degradation during epidermal differentiation.
- Desquamin's specific RNAse activity suggests a role in regulating RNA during terminal differentiation.