  We define a kind of 'operational calculus' for $GL_2(R)$. Namely, the group
$GL_2(R)$ can be regarded as an open dense chart in the Grassmannian of
2-dimensional subspaces in $R^4$. Therefore the group $GL_4(R)$ acts in $L^2$
on $GL_2(R)$. We transfer the corresponding action of the Lie algebra $gl_4$ to
the Plancherel decomposition of $GL_2(R)$, the Lie algebra acts by
differential-difference operators with shifts in an imaginary direction. We
also write similar formulas for the action of $gl_4\oplus gl_4$ in the
Plancherel decomposition of $GL_2(C)$
