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Expression of microfibril-associated glycoprotein-1 (MAGP-1) in human epidermal keratinocytes
N Fujimoto1, S Tajima, A Ishibashi
1Department of Dermatology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan.
Abstract:
Microfibril-associated glycoprotein (MAGP) is a major structural component of connective tissue microfibrils. We studied the expression of MAGP-1 in cultured human keratinocytes and its modulation during Ca(++)-induced differentiation. RT-PCR and Western blot assays demonstrated the presence of mRNA and the polypeptide of MAGP-1 in cultured keratinocytes. MAGP-1 mRNA levels in cultured keratinocytes during Ca(++)-induced differentiation were enhanced eightfold with a concomitant increase in involucrin (a marker of terminal differentiation) mRNA levels. Double immunofluorescence labeling of cultured keratinocytes demonstrated that both anti-MAGP-1 and anti-involucrin antibodies reacted with the identical cells. The population of MAGP-1-producing cells in cultured keratinocytes significantly increased during Ca(++)-induced differentiation. These results indicate that MAGP-1 expressed by cultured keratinocytes reaches maximum levels at the stage of terminal differentiation in vitro. Double immunostaining of normal human skin with anti-MAGP-1 and anti-elastin antibodies demonstrated the colocalization of MAGP-1-positive and elastin-positive fibers in the superficial and mid-dermis. MAGP-1 produced by keratinocytes may play some functional role in the formation of dermal matrix organization in the dermis.
Insights
Microfibril-associated glycoprotein-1 (MAGP-1) is expressed by keratinocytes and increases during differentiation. MAGP-1 may play a role in organizing the dermal matrix in human skin.
Area of Science:
- Biochemistry
- Dermatology
- Cell Biology
Background:
- Microfibril-associated glycoprotein (MAGP) is a key structural component of connective tissue microfibrils.
- MAGP-1's role in keratinocytes and its modulation during differentiation are not fully understood.
Purpose of the Study:
- To investigate the expression of MAGP-1 in cultured human keratinocytes.
- To examine the modulation of MAGP-1 during calcium-induced keratinocyte differentiation.
- To explore the potential role of keratinocyte-derived MAGP-1 in dermal matrix organization.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) to detect MAGP-1 mRNA.
- Western blot analysis to detect MAGP-1 protein.
- Calcium-induced differentiation of human keratinocytes in culture.
- Double immunofluorescence labeling and immunostaining to assess protein localization and co-expression.
Main Results:
- MAGP-1 mRNA and protein were detected in cultured human keratinocytes.
- MAGP-1 mRNA levels increased eightfold during calcium-induced differentiation, correlating with increased involucrin mRNA.
- MAGP-1 and involucrin were co-expressed in the same differentiating keratinocytes.
- MAGP-1-positive fibers colocalized with elastin-positive fibers in the superficial and mid-dermis of human skin.
Conclusions:
- MAGP-1 is expressed by human keratinocytes and its expression is upregulated during terminal differentiation in vitro.
- Keratinocyte-derived MAGP-1 may contribute to the organization of the dermal extracellular matrix, potentially interacting with elastin.