Histology USMLE Step 1 Practice Question

A 54-year-old woman presents with a 2-month history of recurrent, painful erosions of the oral mucosa and a 1-week history of flaccid blisters on the flexural surfaces of her trunk. Physical examination reveals multiple ruptured blisters with thin, friable roofs in the axillae and groin, along with erosions on the buccal mucosa and soft palate. A positive Nikolsky sign is noted on the skin. Histopathologic examination of a perilesional skin biopsy demonstrates acantholysis with intraepidermal blister formation at the level of the stratum spinosum, with preservation of the basal keratinocytes. Immunofluorescence microscopy reveals intercellular IgG deposits in the epidermis. Which of the following cell junction components is the primary target of the autoimmune response in this patient?