The molecular architecture of hemidesmosomes as revealed by super-resolution microscopy

Abstract

Hemidesmosomes have been extensively studied by immunofluorescence microscopy, but due to its limited resolution, their precise organization remained poorly understood. We studied hemidesmosome organization in cultured keratinocytes by 2- and 3-color super-resolution microscopy. We observed that in the cell periphery, nascent hemidesmosomes are associated with individual keratin filaments and that β4 is distributed along rather than under keratin filaments. By applying innovative methods to quantify molecular distances, we demonstrate that the hemidesmosomal plaque protein plectin interacts simultaneously and asymmetrically with β4 and keratin. Furthermore, we show that BP180 and BP230 are characteristically arranged within hemidesmosomes with BP180 surrounding a central core of BP230 molecules. In skin cross-sections, hemidesmosomes of variable sizes could be distinguished with BP230 and plectin occupying a position in between β4 and BP180, and the IF system. In conclusion, our data provide a detailed view of the molecular architecture of hemidesmosomes in cultured keratinocytes and skin.