  We consider the influence of disorder on the non-equilibrium steady state of
a minimal model for intracellular transport. In this model particles move
unidirectionally according to the \emph{totally asymmetric exclusion process}
(TASEP) and are coupled to a bulk reservoir by \emph{Langmuir kinetics}. Our
discussion focuses on localized point defects acting as a bottleneck for the
particle transport. Combining analytic methods and numerical simulations, we
identify a rich phase behavior as a function of the defect strength. Our
analytical approach relies on an effective mean-field theory obtained by
splitting the lattice into two subsystems, which are effectively connected
exploiting the local current conservation. Introducing the key concept of a
carrying capacity, the maximal current which can flow through the bulk of the
system (including the defect), we discriminate between the cases where the
defect is irrelevant and those where it acts as a bottleneck and induces
various novel phases (called {\it bottleneck phases}). Contrary to the simple
TASEP in the presence of inhomogeneities, many scenarios emerge and translate
into rich underlying phase-diagrams, the topological properties of which are
discussed.
